Cooperation in team fights:
The team support skills are in the game, I just hope the effects are powerful enough that players don't just use them continuously for extra damage, or ignore them entirely in favor of builds focused on damage and personal survivability.
At the very least walls, ground heals, and condition removal are all skills that should be more effective in the hands of a player that watches the whole battle instead of tunneling one target, and that's important to me. Hopefully those skills are an integral part of high level combat.
In this regard there are two more things I'd like to see added:
1. A few ground target heals that do their healing instantly instead of forcing you to stand in one spot. Standing still in a geyser for 15 seconds isn't really practical in pvp. Also self healing should be toned down a little bit, and group healing buffed up across the board. Some self reliance is great, but I think players should be rewarded for watching their teammates backs, and not just their own skin. This doesn't mean that one player has to be "the healer", or that total healing (combined team healing and self healing) has to be increased compared to what it is now though.
2. Some CC that breaks on damage and has a longer effect than stuns/kds. These skills encourage players to do more than tunnel vision one target. Instead of just unloading all your blinds, stuns, kds, cripples etc on the target you're attacking (might as well in most cases), you need to simultaneously control one player while damaging another. This kind of multitasking and split-awareness is my favorite part of MMO combat. It also discourages recklessly spamming aoe damage and rewards players for communicating and coordinating what targets they are attacking.
Both of these things would encourage players to be more aware of the entire scope of a fight, instead of just tunnel-railing one target into the ground or throwing out as much aoe damage as possible.
I love the pacing and movement, and the skills seem to be designed with skillful and creative uses in mind. The skills in GW2 are basically a wet dream for 1v1s or 1vX fights, and those fights are going to be really fun regardless. I just hope the team fights don't play like a 1vX with allies 1vXing around me. I want to be coordinating and cooperating with the other people on my team, not ignoring them.