Never ever ever ever do any type of large quest or mission that involves multiple people without doing your homework first. If you always do your research first it will save you a lot of grief later. When you are doing things like AF quests and request some higher level help only to show up and realize you missed a step in flagging it or don't know where to go you may find yourself stranded and on someone's /blist.
For Eco specifically, you should stay together. People tend to like to play hero and if there are mutliple mobs everyone will try to solo one. Avoid this by having everyone attack the same mob. The faster each mob goes down the less mobs there will be beating on you. I'd suggest /assist macros but considering some of the lesser Dynamis groups can't manage it I would assume that a pick-up PT of low level plays wouldn't have a chance.
Communication needs to be solid and the group really needs to agree to work together. If one person wants to pretend to be a badass or has a bad attitude it's better for the alliance leader to kick that person rather than wait for them to do something stupid like train monsters on the group.
Another note is that you should all gather at the person that reduces your level cap to 20 and let everyone know to get it. The may require several spammings of the chatlog in all caps with calls. It's annoying, but it's far more annoying to have to backtrack because 1 out of 18 people wasn't paying attnetion and didn't receive the cap. If this happens it may be best to drop that person from the alliance. It sounds harsh but like Lionx said.... people are pretty impatient, especially at lower levels. Backtracking will cause people to start dropping out quite often.