Our first problem was positioning. I think we've gotten that part taken care of. I also HT + RoT Phase 1 and single-target the rest of the encounter, I was speaking vaguely before.
Our transition from phase 2 --> 3 could be better. We still have the last soldier and knight at about 25%-40% HP when 1st Dreadnought drops. We get through it and kill the big guy, but the next phase with the bugs + the guys that cast Pox (can't remember their name atm) take too long, usually because they are too spread out and not taking all AoE. TP has been an issue a time or two as well. I think we'll get it; we've only attempted on 2 different occassions. Unfortunately, we're spread across PST, CST, EST, UK and Aussie time zones, so coordinating is hard as hell and we won't get another chance for about 2 weeks. Boo.
Speaking from the Dreadnaught tank perspective, once the first one dies just collapse all the way in the center again and stack up. Rooks don't really hit hard at all and whoever has hate just faces them away. Plus, don't worry about having health left on at least the last solider/knight as it's normal for working through it: if it's the melee mob the BLM can just shift to the Dreadnaught and start on it, and if it's the caster mob you as the DRG can shift to the Dreadnaught to get started (debuff and whatnot) while your three ranged finish it off.
We actually split our damage on the double knight/soldier/P2 so the DRG's on the OT's magic guy and the other three (MNK, BRD, BLM) work on both of my mobs, blow something up the second a stoneskin drops, and then clean up. I think we still have about 40% left when the Dreadnaught drops which is fine because that gives me time to feed him all four bugs and build a bit of hate as any damage dealt to the Dreadnaught prior to feeding is pointless since he just heals.
Phase 4 (Rooks and bugs) is a good time for one of the bards to pop Paeon for about 20~ seconds. He can still AoE and boost the other bard's and yours TP regen rate, while the BLM does whatever AoE rotation he prefers. If you have a bug or two still left (like 10-15%) when the Dreadnaught drops don't worry about it since you've got stuff to kill in the center first on Phase 5 anyway before you move on to the big guy.
Hopefully mana's not an issue with your healers (make sure your tanks aren't flashing knights and soldiers!).
You guys sounds fine, just in our same boat we're having with Turn 5 -- attendance and barely getting in a night a week. It's the only thing sucky about MMOs around holidays for endgame groups.