Why Escorts, Tacs, and DHCs work so well
 

Efficiency & Synergy

Damage Output
Efficient: The DHC/Turret combo gives a ship the most 'power dain' efficiency as your heavy hitters are firing at full or near full strength while your low damage weapons are hit with the brunt of power drain penalty. No other weapon setup is as good at mitigating the damage loss from this mechanic.
Synergy: Damage output follows a simply rough formula. (Total Base Damage * Critical Modifier * Damage Multiplier * Recharge Modifier) + Bonus Damage * Target Resist Multiplier. Total Base Damage is modified by weapon, +% consoles, captain skill, and Tactical Team. Critical Modifier is obvious and modified by Attack Pattern Alpha. Damage multiplier is modified by Attack Pattern Alpha, Omega, Go Down Fighting, Epower to Weapons, and Tac Fleet. Recharge Modifier by Rapid Fire. Bonus damage are weapon procs or Directed Energy Modulation. And Target Resist by AP Beta/Delta and Fire on my Mark. As you can see all those effects and abilities when combined become greater than each would be on it's own as they all multiply and create a synergy bonus that nothing else in the game does. This allows us to kill stuff fast.

Power
Efficient: An escort has very simply power requirements that are covered by it's inherent bonuses. It has enough engine power to hit bonus defense cap and so much weapon power it is free to shift some into shields. Finally it has little need for additional Auxiliary power as it will typically only have one to three abilities that use it and will have around 50 inherently anyway.

Survivability
Efficient: Avoiding damage is the most efficient option and the escort is the top dog. But beyond that the next most important part is high resist values relying primarily upon 2-3 armor consoles and the much loved ensign ability Emergency Power to Shields that an escort sacrifices very little to take. The final important factor is survival is healing and while the escort does have a minor penalty to innate shield regeneration they do receive the same exact amount of shield/hull from a boff ability as any other ship would. In the end the difference in the survival efficiency of the ships/setups they are so close it is splitting hairs. Finally having more survival at the cost of damage output than necessary is inefficient.

Cleansing
Many of the most frequently used debuffs by the NPCs are negated by Tactical Team and Attack Pattern Omega. E-Power to Shields and Hazard Emitters, both abilities an escort sacrifices little to have, remove all but a few of the remaining effects.In addition Tactical Team increases damage, and keeps you alive. Attack Pattern Omega increases damage and survivability significantly as well. These abilities are never wasted and always useful.

Skills
The skills desired for this are always on always useful. You do not need to worry about those six ranks of subspace decompiler that effects nothing on your setup when changing ships. Nor about taking aggro constantly with a skill such as threat control. Damage is always good, and every ship has weapon slots.

Conclusion
While at the lower levels ship types do seem to have better defined limitations when you get to VA many of those disappear for the tac DHC escort captain. He still gets to have high resistance rates on his shield/hull, a fair amount of healing and cleansing, and at the same time his damage capability increases in a multiplicative manner. By comparison the engineer cruiser finds his offensive options nearly as limited as at early levels and begins to suffer diminishing returns on his hull resistance and little need to boost shield resistance or healing as far as he can. Similarly the Sci/Sci begins to finally see many nasty options at his disposal but lacks the capability to truly focus on more than one. Yes yes these are generalizations but I honestly ask you does any combination in the game scale as well as this one?

Don't forget ability synergy. If a sci captain throws all his captain abilities on at once, he'll throw out an energy-damage-reducing field here, strip buffs there, summon decoys over there, and so on. Lots of tricks, but they don't much build off each other. Engineering captains are similar, with rarely a reason to pop off EPS Transfer, Nadion Inversion, and Miracle Worker all at the exact same time. With a Tac, APA + FOMM + GDF + Tac Fleet, they directly compliment each other into one killer package deal.

On BOFF abilities, its largely the same story. Sci powers give you lots of options but rarely work together (some do, maybe 2 powers in combination once in a while, but not usually). Engineering, same as sci, a bundle of mostly-independant abilities. Tactical? TT + CRF + THY + APO = boom.

Honestly I think that synergy might be a bigger single reason than anything else.

That was a very interesting breakdown on Escorts and their capabilities in the hands of a tactical captain. I agree with almost everything you said, and what I don't agree with isn't worth bringing up. But... it's a DPS based game (as PvE goes anyways)... and what do Tactical captains specialize at? Tearing faces off. What are escorts good at? Tearing faces off. Apples + Apples = more Apples. Until PvE end content changes away from pure DPS (which is a good way for PWE to lose money, so it will never happen), tacscorts will always be the most effective ships for PvE.

I'll post a different angle on weapon efficiency, probably most over looked by others.

A tac escort's forward firing arc, while powerful is all about large bursts of damage. The raw damage isn't totally out of balance with other classes, but the ability to quickly take out a single shield facing and then hull, destroying a ship is VERY efficient.

So if a tac cruiser using fire at will flying through enemies throwing out 4k dps (respectable cruiser DPS for sure), a sci escort will throw a similar 4k DPS but will be far far more effective. The cruiser will hit multiple shield facings, and face enemy shield balancing, regeneration and hull healing as it takes longer to kill an enemy, the escort just hits from one vector, killing and bypassing enemy healing.

It did change. HOE is very conducive to a mixed captain environment. The problem is the average player in this game is so terrible that they can't handle an environment that challenges you to play properly within your class roles.

What's cryptic suppose to do? When they make content more difficult so that control, rebuffs, support, and survivability are key; people whine and complain the content is too hard. When they make it too easy, then the Eng and Sci pilots complain they are undervalued (and they are).

Can't have it both way folks. Either the game needs to get harder or tac/escorts will remain dominant.

It should be harder, at least at the top end. Compare the number of mechanics in an entire Elite STF with the number of mechanics for one wow raid boss http://www.wowpedia.org/The_Spirit_Kings

Additionally, the raw difficulty is pretty low. I've finished ISE with six minutes left on the timer, and I'm sure someone can do better. The only content that has difficulty is Hive and No-Win.

This is simply not true. The more difficult you make the content the more important efficiency becomes. Cruisers are 'hybrids' they are not the most efficient at anything not healing not tanking not cc nothing. They do it all, and do it all well enough for most, but they are not the best. Increasing difficulty will simply make the problem more obvious. The only role that escorts are not the most efficient in are healing and energy drains that's it. But I'd rather not get into that here.

However they have created two new pieces of content that DO manage to avoid this issue. Starbase Blockade and Azure Nebula Rescue. Those missions are designed around completing an objective and you are free to do so in any manner you choose. You can heal, tank, destroy, cc, or a combination thereof. That style of content does allow a hybrid to shine.

Thing is most of this game is single player. Building a solid heal/support ship is pretty useless if you spend most of your time as the only friendly ship in a map, and in the end you still need to do the killing yourself. And as for STFs, they're DPS oriented and I want to have to depend on and coordinate with my questionable teammates as little as possible, certainly not expect them to fit into some predefined role or be myself so pigeonholed. For the most part this is not a team game, and insulting other players for not playing how you think they should serves no purpose.

Actually, it comes from a quirk in the way boff powers/captain powers interact addatively.

Lets say I have an ability which makes me fire twice as many shots, with each shot fired at 75% of the strength of a normal shot. That power would look like this as a standalone ability:

Normal dps * 0.75 * 2 = 1.5 * normal dps

And lets have another power that increases the rate of fire by 20%, and the damage of each shot by 25%. As a standalone ability which will look like:

Normal dps *1.25 *1.2 = 1.5 * normal dps

Ok, so these two look balanced relative to each other, right?

Ok. Now lets interact this with a power that increases all my damage by +25%:

Version 1 - Normal dps * (0.75+0.25) * 2 = 2 * normal dps

Version 2 - Normal dps * (1.25+0.25) * 1.2 = 1.8 * normal dps

Now lets go silly and stick several modifiers in that total, say, +100%:

Version 1 - Normal dps * (0.75+1.00) * 2 = 3.5 * normal dps

Version 2 - Normal dps * (1.25+1.00) * 1.2 = 2.7 * normal dps

Cannon rapid fire and torpedo spread are both powers that get to exploit this mathematical interaction and tactical captains get a large range of positive damage modifier powers to play around with.

A sci ship with sensor analysis and with the ability to fit cannons can produce a similar interaction effect with cannon rapid fire. The strength of that build would be having pretty much no downtime other than the first few seconds of building up to full strength sensor lock.

No. Go tell the PvP folks how terrible cruisers are in their roles and that they are "hybrids". Flying them as a hybrid is a sure fire way to mediocrity though.

Survivability is a premium in HoE, because 2 of the objectives are based around it. And cruisers bring more group survivability than any other ship type.

Bottom line, your not flying it right. You can either make them as pure support boats who's healing capacity outstrips all other ship types, or you can make them into aggro magnet that can tank and do respectable damage. Both are quite useful in HOE.