Going to mainly talk about two different dreadnought build here and will also discuss some "do"s and "don't"s when flying a dreadnought. Wall of text alarm.
Beam array DN:
Front: 4 beam array (or 1 DBB+3 beam array)
Back: 4 Beam array
Console: Tact - 3 X damage specific console (will be either phaser or AP, will dicuss different later)
Engi - Shield Generator, 2 X neutron. alloy, 1 other of your choice (personally will go for 3rd
neutron for pve, and cloak for pvp)
Sci - Borg assimilated module, Enhanced plasma manifold (for free player, just swap the EPM for
other thing you like, won't make much a different since most sci console make hardly any
BoFF: must have skill - EPTW (preferable rank 1 X 2 since you can cycle them, not only give u 10%dmg,
also it can help you reach 135 weapon cap very easily)
ET, RSP (rank 1 will be ok, some ppl run 2 RSP, that's ok too, but since you can only
use 1 every min, i think 1 is enough for critical situation.), EPTS, DEM (work great
with BFAW, 1 is ok, 2 work as well, but will reduce survibilty a bit), BFAWX2 (Rank1)
optional skill - ST, TT, PH, TB, APDelta, BOverload
Front: 1 DBB + 3 cannon
Back: 4 turret
Console: same as above
BoFF: simliar to above, but you will want to go for more dps oriented than beam array type, I will dicuss why later. Just swap the beam skill with CRF, keep Boverload if you want to run burst DBB (or throw in a Target shield/weapon), otherwise just go for TT.
"Do"s and "Don't"s
1. IMHO Dreadnought shouldn't equip torp. Because first of all, you don't turn very well, you are ok in pve since most AI are stupid, but in pvp you will find it is much harder to line up that 90 degree arc not to mention if your target shield is up, you will do very little damage. Beside that you can free up tons of skill points if you don't torp at all, and that will benefit into way better survibility.
2. RCS, I never like the idea of putting RCS on a DN. Because even with multiple RCS, you will never turn like a escort or ligher size cruiser, if one of those is on your butt, doesn't matter what you do, u will not be able to shake it off doesn't matter how many RCS you have. On the other hand, putting Neutron alloy give you 24/7 defense (1 = about 18%, 2 = 30%, 3 = 36%).
3. Phaser or AP? TBH you can't never go wrong with phaser on a DN, since your lance is phaser damage, and phaser is very good pvp energy type. But that doesn't mean AP isn't good at all, AP give you about 2-2.5% extra overall damage (since it give 2.5% crit chance and at end game, your crit severity is close to 100% with skill and weapon bonus), but on the other hand your lance won't hit very hard, so it is kind of trade off in between steady dps vs burst dps. Personally I go for phaser since I don't need to swap weapon for pvp.
4. Boverload is it good? Well, lots of ppl will think, hey the answer must be yes. Well I found that to be very situational. First of all, since you are running 8 energy weapon on your DN, your weapon level could drop as low as 7x when all things are firing. If you add a 50 weapon cost BO on top of that, after each BO fire, it take at least 2 cycles of attack in order for your weapon power level to go back to the normal range. That mean you are dealing sub-par damage for 2 full cycles. So it pretty much go back to the same drawing board where "steady dps vs burst dps", there is no certain answer to that, it really just depends on your play style or what you need in certain situation.
5. DBB or just go for 4 x Beam Array: same as above, if you want to run BO, then sure feel free to fit in a DBB, but if you just want good steady dps, 4 Beam Array is good as well since your BFAW will give you better steady dps.
6. Beam Array vs Cannon: each has it's pro and con. For Beam Array, you will have a very easy time when you boardsiding, it is very easy to maneuver; but it does less dps than Cannon build since skill like DEM and CRF work better vs single target. For Cannon, it is easy to maneuver as well, but if someone is at your butt, you will be dealing less damage than Beam array build (tbh, not like it matter at all), it has superior single target dps, but BFAW will do a lot more damage to multiple targets(BFAW does good damage to single target as well, but just not as good as CRF especially when you have DEM on). For pre-made pvp, I would go for cannon since you will be bursting a single target most of the time, but for pug pvp where people just random shoting at things, BFAW will help you top the damage chart everytime I promise (since you can cycle 2 BFAWs, which mean you can BFAW every other 10 sec)
7. Tact. Engi or Sci? First of all, DN is not a support ship at all, it's role is like a "tank" (not tank in MMO terms, but tank in real life terms). You can take lots of hit while doing very good damage. But it act poorly when you try to support others, so you should either choose to do either hitting hard or tanking good. So I am just gonna dicuss Tact. vs Engi here. For Engi, obvious you will have better survilibity, but at what cost? 90% of time at end game (both pvp and pve), you either tank easily or you can't tank at all. Engi. DN can tank 3 or even more borg spheres in Elite STF, so does a Tact. DN. Tact. DN (or nobody) can get 1 shoted by a Elite tact. cube, so does Engi. DN. You won't find significant different in survibilty between a Tact./Engi. DN in pve. For pvp Engi. does survive little better than Tact., but still nobody can survive if 3-5 ship is focusing on you. On ther other hands, Tact. does significant damage compare to Engi. especially in pvp when bursting down someone is No. 1 piority. I personally will go for Tact. DN very time, but some ppl may prefer to be an Engi. DN and that's fine, just play style differences.