well you have to keep pulling groups especially with hechies. That's my suggestion. Take out enemies group by group. Ok to pull with hechies is fairly simple unless they don't follow you...lol. To do this, before you aggro a group click on yourself, then aggro the group. When you see that the enemies are starting to chase you press "X" and press CTRL + T + spacebar (sometimes you have to do this 2-3 times before the hechies listen). Run back a little and the hechies should be running after you instead of engaging the enemy. When you have a little space from the other group then engaged them. I've played a lot with hechies due to the fact that when I play everyone in US is still sleeping so i really dont have a choice. Anyway hope that helps.
Remember to zero in on enemy monks, then eles, then mesmers, and then the warriors. Usually PvE enemy rangers cause little trouble. Of course it doesn't have to be the exact order. Just use whichever works for you.
Now for going with other humans I always say there should be a target-caller so you take the enemies faster. If no one else is calling target then go ahead and do it. Let's just hope they know how to press "T" and listen to you. hehehe.
Well hope that helps. I also hope I answered it correctly. lol.
