Some suggestions, based on what I am seeing, experiencing and reading.
1. Something needs to be done to address party balancing in the queue. I was no fan of tanks and healers getting instant queues in other games, but conversely, I just spent 45 mins trying to get a group of something other than rogues, great weapon fighters and control wizards. Although part of that problem is likely related to my next observations and suggestions.
2. Clerics need Righteousness gone and the aggro bug with how much threat they generate dealt with, because players are shelving them. I think this was why as mentioned above we had so much trouble finding a cleric for our party.
3. GF's need their guard meter quintupled or removed all together (flanking them, or attacking from behind still gets through) because it depleting with one or two hits is pointless. They also need a more solid way to generate threat and punish monsters...like a slow debuff and a dot against any marked target that isn't attacking the GF. Marks need to last until the mob hits the GF, but not fade on their own. I would also say up their threat, but that may fix itself if cleric threat gets addressed.
4. GWF's need to be dedicated to a role. Hybrids do badly in MMO's especially when boiled down to efficiency by players, and GWF's don't fill the tank or dps roles better than classes dedicated to those roles. Maybe replace the class entirely with either the Slayer from essentials who was much more of a stiker than a GWF is (they use defender mechanics, not striker). Or even just go all out and turn them into Rageblood Barbarians instead (full on 4E striker). Change their mechanic to Rage instead of Determination. Where they sit now, they are in limbo about the role they should fill.
5. Up the performance of Regen and Life Steal, make companions more reliable. We already have companions to help address not having a party when we are solo. Make them more valuable in dungeons so group composition makes Clerics and GF's less required (still fix them so they are desired though), thus allowing parties to proceed in almost any composition.
6. So more options for progression exist than just PVP and PVE Dungeons, how about making Foundry missions at level cap, or maybe Spotlighted ones, drop Drake/Unicorn coins for completion (The type of coin dropped determined by GS, if it would be high enough for an epic t1, drop Unicorn, if Epic t2, Drake). Motivation to play foundry coupled with slower but steadier progression option.