The honest answer to your question Zakarn is that it is probably too late to change the things people are unsatisfied with. At this point it would probably require an overhal as drastic as the one they're almost finished with. We're getting what we're getting and the best they can do is tweak this or that to make the pill easier to swallow so to speak.
As far as nailing it down to one specific item, the problem there is that it isn't one thing it's a host of things. And they're all unavoidable core mechanics that can't just be avoided or changed to suit everyone's palate. The WoW styled combat with moves on a GCD, the fetch questing, hand holding from cradle to grave, all the things that could make it another SWToR or AOC. Another game that feels and plays just like WoW that people will try for a month or 2 and walk from.
On top of that issue, differing palates means that some folks are ok with some of those aspects and not ok with others. I'm sure if I look in the "This isn't FFXI and never will be" thread in the Alpha forums there will be someone loving every scrap they've borrowed from WoW and still bemoaning the fact that they even so much as copied the look of the races from FFXI because they hated the game so much.
Edited:
Well, on the topic of questing. Perhaps people wouldn't be so fussy about it if there were a viable alternative. I don't mean something faster per se, just something comparable say within %10 plus or minus of quest grinding. I could see a number of things working that way. Mob grinding either solo or in a party, or chain running instances.
For combat maybe taking another hint from WoW would be a positive thing. It seems like currently every non mage class will be working off of TP. TP currently regerates like energy (used to) for a rogue. Just a set amount regained over a set period of time with no influence over it's rate of gain. You're not really managing a resource, just tapping it out and then waiting on regen.
Tack on the fact that this looks like every non caster classes' mechanic and imo it makes things pretty bland. I would think it to be in their best interest to vary things a little bit more. Maybe have some classes start at 0 and build TP the old fashioned way (smacking something). Maybe give them a quick TP building move they can use when they're tapped out.
Just some thoughts off the cuff.