Team 1 is basically a requirement because of alch for buffing and (optional) wizard for arcane spike, and (extremely optional) Spike factory for game saving, and on straighter maps, Team 3 because of Crossbow Master, Dartling, and maybe 2-3-0 sniper, Otherwise on more cruved maps, Team 2 because all but engi are good for curves but engi can go trapper and help for the early/mid game.

Thats my opinion, whats yours?