Hmm, on 25m trash we just pull the mobs that cast the aoe from the other mobs. I (Feral Druid) tanked all of the melée mobs, by running into the group of mobs aoeing while the other tank (warrior) got MDs to get the casters on him. Single targeted the commander (when there was one) then the melée mobs and then slowly pulled 1 mob at a time from the other tank so that they wouldn't all aoe. I know that the caster mobs can be stunned so I also assume that all of the others, maybe except the commanders can also be stunned. We used 5 or 6 healers.
Important points to remember:
Melée mobs cleave
Casters aoe when more than 1, maybe more than 2 people (INCLUDING PETS)
Have the tanks spread out
Using CDs effectively ftw.