I... I don't know.
After experiencing 5 different MMORPGs I've come to the realization that there may be some inherent things in the style of game that can't be fixed, foremost the human factor. Not that I don't still enjoy SWTOR, but it's definitely a more single-player/story focused one than most.
Lots of MMORPGers like PvP, yet the combination of lag and poor teamwork and communication skills usually guarantees a miserable time for the losing team. Lag is likely a major part of the reason why most MMORPG combat is usually so boring and simplistic compared to a single-player game, since you must try to allow for the slowest connections possible. I don't mind sub-par graphical fidelity to compensate, but a lot of people do.
People say they want to eliminate the grind, but if it was all story quests you'd be able to finish it in a week. You should want to go out and explore the world, find new places and missions. If you're impressed by a new area or a raid boss' attack, you're probably going to get distracted and die since it's your first time, prompting abuse and kickage shortly after. Unlike a single player experience, where you could use trial and error for things and take your time to explore the environment. Days after new content comes along you are expected to know it inside and out (many is the time I've seen the cry of 'SPACEBAR!' to hurry text along even if it's a player's first time in a Flashpoint).
Maybe the party system in GW2 is a partial solution, at least outside of dungeons. You're automatically part of an area-wide party the moment you step into it and you can't really sabotage everyone else's questing. You can see player's locations and know wherever there's a gathering there's probably a group mission going on that you can help with if you like. I forget if this is the case in GW2, but in SWTOR every class has at least one support ability that can contribute to a group beyond the chosen role (beyond the unique buffs, Jedi Sentinel gets Transcendence, which can be used after striking enemies a certain number of times that significantly boosts the entire party's attack power for 10 seconds and can be used often at high levels). I'd like to see more interlinked class benefits like in Team Fortress 2, where a party of 3 people is automatically far stronger than 3 individuals due to the benefits each one can provide for the other. I liked City of Heroes' combat too due to the huge variety of abilities used by both the players and enemies- it probably has the most diverse (and some of the most difficult) enemies I've seen in a MMORPG. The Yakuza-style Tsoo gang had a bunch of enemy types that pretty much copied the common player roles and had to be approached as such, and this is only at level 20- there were other gangs with even stranger talents.
Anyway now I'm just rambling on now about good past MMORPG experiences, and with work I don't really have the time for major commitment to an MMO anymore anyway. Theme-wise, I've dreamed of a feudal-style MMORPG where both demons and the armies of enemy warlords are your opponents, perhaps beginning with you doing tiny intro fetch quests for people around your town, getting to know them before your town gets burned down by a rival warlord seeking to become Emperor. You survive, and are trained by your nation's military to defend your realm from enemy fiefdoms and demons. Another thing to borrow from Eastern RPGs- the inclusion of a 100-floor gauntlet dungeon that requires endgame gear and levels to complete. If something like this came out and got positive reception, I'd ditch SWTOR for it.