Immediately following each successful capture or defense of the Wintergrasp fortress, a number of 10 and 25 man VOA groups start to form. I've been a involved in quite a few of these, and they have the highest failure rate of any PUG, anywhere.
The following are some general guidelines I've come up with on how to increase the chances of a successful PUG.
- Before each boss, explain the fight. Don't ask if anyone needs it explained, just do it. In any large PUG there are bound to be a few people who don't know the fights, but who are unwilling to admit to it lest they appear to be a noob. (I've never had that problem, but I'm less shy that way.)
- Remind people that this is a PUG, and to expect a few wipes, and to be patient. Ask people to commit to a minimum of four attempts. If at that point the group is clearly not getting it, is not improving on each attempt, doesn't have high enough DPS, or generally appears doomed to failure, then go. But don't be such an impatient and arrogant fool to expect that your PUG is going to be the magical one that manages to down the boss on the very first try.
- Keep it moving! One of the largest attrition factors I've found is the delay between attempts. Get everybody right back in, get rebuffed, and go. Maybe take a minute to discuss what went wrong, and to change assignments if necessary, but make it quick. Don't debate endlessly. Take too long and it will appear that you simply have no idea what you're doing. People will get bored and start to leave.