Best team possible [H][PvE]

Hey I been wondering lately, if i wanna dip into the whole mbox thing for PvE only!

- I want to clear dungeons and possible raids/trash, and later on old content when TBC/WotLK arrives.
- I dont mind having different teams for specific content, if that could become an issue.
- I dont care about "fun", i want the absolute best team possible (except, going alliance)
- I care not for PvP so that shouldnt be a consideration at all.

What is the best 3 teams i could make?
Also if they are expansion specific ?

Thanks in advance.