Klink ships are not overpowered, with the possible exception of universal stations. In fact, I find them rather easy to destroy, as long as the rest of the team has some decent pvp experience.
I do wish some newer pugs wouldn't full impulse towards the first thing they see (usually a tanking carrier). I've played enough FVK to know exactly what happens. One or more ships break formation and full impulse to help them (with the rest of us screaming "NOOO!"), he/she's destroyed before they get there, the rest of them decloak and pick us off one by one.
Or worse, finding yourselves in a team that think immediately full impulsing to the opposite side of the map, "to find the Klingons", is a good idea.
Wow, never thought I'd hear a klingon say that. I'm in an assault cruiser, and my most powerful heals are engineering team and extend shields. Hazard emitters are good, but don't top the insta-heal of ET. Correct me if I'm wrong, but I believe Transfer Shield Strength uses auxillary power, which seems to me to be a distraction from better options. As far as your extra engineer spot, I'd use EPtS, you'll thank me if you ever fight DOB, lol.
The one thing I don't believe you're taking into consideration is that you have a 50% better turn rate than a fed cruiser. Since staying withing 5k is so important, this limits the feds ability to stick with allies, and keep them alive.
PS. On a side note, the only klingon ship I've never been able to solo is the Battlecruiser. Better DPS, first strike, more maneuverability, and virtually the same abilities, equals dead fed cruiser.
You're forgetting that teams all share a cooldown though. Once you're running 3 teams, adding a 4th or 5th is a bit of a waste. I can sometimes be useful to have that extra team, but the times when you already have your other teams on cooldown, need something right now, and can't wait the extra 4 seconds for another team to come off cooldown are pretty rare.
EPtS is useful, but again, using it more frequently isn't that big a benefit.
There are only 4 useful engineering abilities, and 3 of them share cooldowns with other frequently-used abilities, so between the Commander and Lt. Commander stations you probably have as many copies of each as you can use.
When everything is going pear-shaped it's usually better to have another ability on a completely different cooldown, especially when you're already using 3 or more abilities on the same shared cooldown. The issue isn't that engineering abilities are bad, only that there aren't enough good ensign engineering abilities and that the 2 you have are likely to share cooldowns with higher-rank abilities. The good Engineering abilities are *great*, but there isn't enough variety for the extra ensign slot to be necessary.
While I could take or leave an extra Tactical ability, an extra ensign Science ability would mean an extra heal/buff on a completely different cooldown.
I do think that the better turn rate is a big advantage, but not for healing. I've got a tier 4 Fed cruiser with a very similar set-up to my Klink, and the super-crappy turning doesn't make a huge difference where healing is concerned. On either one I occasionally need Evasive Maneuvers or a battery to position myself, and there doesn't seem to be a big difference in how frequently my regular turning is insufficient. Either way I'm pretty much just orbiting the fedball while firing wide-arc weapons and keeping my attention on whomever is being focus-fired.
Where the maneuverability is a huge advantage is in DPSing, because it's actually possible not only to mount dual-cannons on a Battlecruiser, but to actually be able to turn and keep them on target. But for a healer, front firing weapons seem to be wasted since you spend most of your time maneuvering from one friendly target to the next.
I don't really know if my Battlecruiser can solo a Fed cruiser; the fight just goes on too long to stay 1-1. Usually I just keep steaming towards my team, because my damage is less than 1/4 of my healing so other cruisers take like 15 minutes to kill. With different bridge officers, weapons, and consoles, I'd probably smoke a fed cruiser 1-1, but while I was screwing around the BoPs and Raptors would be exploding like piņatas.
I don't think my Klink is especially bad or anything, but it's not hugely OP either. Once the fight starts I'm healing so I can't use cannons effectively, and I'm the last person to re-cloak if I get to cloak at all. Usually I end up playing exactly the same as I would on my Fed, with the exception being that I get to shoot first.
I can see where maybe the BoP universal stations are OP, but the BoP basically ends up being a Science-DPSer instead of the Science-tank the Feds get. BoPs are stronger on the alpha-strike, where Science ships are stronger in endurance fights.