I'mma make this simple. The dreadnaught is a fickle beasty. It CAN work, if flown properly with the right equipment. Not many people do fly it properly, which is why so many people say it's underpowered.
I say it's a niche ship. No matter which way you fly it, it needs too be flown with a fleet. Find a group of people, and stick with them, learn how the beauty moves.
I personally recommend the Hakashin build. I've flown it myself. The only downside is it's primarily made for tactical pilots, meaning if you've specced into something else, you're btter off with a different ship. Use the thing as a giant sniper rifle. Put as much firepower downrange as possible, meaning cannons and CRF 1. DEM can help, but I don't ever notice huge improvements too firepower with it. So long as you stick as many of the best phaser relays you can get your hands on into the tac slots, and use a a properly timed bombing run, this thing will eat most weaker hulled starships for breakfast. If you've got a stronger hulled ship your trying too take down, have your team munch on it for a while, then come in and do the same thing to them, decloaking and snapping their hull in two with the lance.
When I used this build, even on mediocre equipment, I would often break through smaller weaker cruisers. Tor'Kahts didn't stand a chance, and escorts were piecemeal prey. I often saw 70-80k + alpha strikes from the lance.
I AM THE HARBINGER OF HOPE!
I AM THE SWORD OF THE RIGHTOUS!
The problem with the Lance is that it hardly ever fires accurately. Sneaking up to within 2km of an enemy's rear and firing the Lance doesn't work either, it missed both times.
I'd say stick with flying a Guramba Siege Destroyer, on the KDF side. The Javelin has a better aim, and deals more damage if properly buffed. I've been able to hit "90k (60k)" when hitting all the buttons.
Depends on what you want to use it for. Personally I love the Gal-X on my Engineer. She's a wonderful tank ship and the Lance is nice for added DPS. I honestly don't get the complaints about the lance missing, seems to hit both times for 10K+ per shot for me all the time. Maybe it's captain skills in terms of points in your targeting?
I've found she works better for me when I run using 6X Beam Arrays and a torp launcher fore/aft. Currently I'm running her with 6X Mk XII Phaser Arrays(purple) and the Rapid Reload Transphasic fore/aft. I'm using the Breen Set until I get the Borg/Omega reputation going and with the buff Transphasics got in the last few months, you can do some nice burst damage with them now, especially with the Transphasic cluster torpedo which I sometimes substitute for a beam array.
Biggest issue with this ship is going to be turn rate, bar none, at least in my experience. That's one of the reasons I run a beam FAW build instead of cannons. I honestly just have too many issues keeping things in the forward arc to make CRF and spread fire viable and even though it can equip dual cannons, unless you are using Evasive to get 7-8 km out and then making a straight on run, the 45' arc makes the duals useless on this barge. Also you really don't have the tactical slots to take advantage of the higher level BO tac powers. I know some Tacs like the Gal-X for DPS but for me she's a great ship and more effective with an Engineer, since you have a lot of extra power to play with through Captain skills. Two neutroniums seem to give me plenty of hull resistance so I slap an RCS and Tachyokinetic Converter(from Lobi) in the other two Engineering slots. I also run auxilary to dampeners constantly to help the turn rate.
With the right bit of TLC this ship can be absolutely awesome, but it takes a long time to sort of play with it to find what works for you.
I like the Dreadnought. My build runs with phaser arrays x6 and one quantum torp on the front (that will probably change in the future) and the Omega Cutting beam on the rear. I use the borg console for the omega weapon buff. I also run the phaser relay for bonus power for the lance. I have noticed an increase in accuracy with the lance when used with a tractor beam. That may just be me though...