This my 300pt. mixed team(no dupes, also I try not mix heroes and villains).

V Bane 85pt.
E Firelord 81pt.
V Doombot 38pt.
E Pyro 35pt.
R Quicksilver 18pt.
E A.I.M. Medic 16pt.
R Vulture 15pt.
R Hydra Medic 12pt.

Bane and Firelord are odviously my 2 heavy hitters and they allow me to do up to 10 damage a turn. Doombot carries Bane around(using Brotherhood free move), and Vulture is Firelord's taxi. Quicksilver really helps as a tie up character to slow down an opponent's high point figure(or a medic, in order to prevent it from using Support), and Pyro is extremely effective in taking out swarm teams by busting up their formation with his Dual EE attacks. My 2 medics usually stay as far away from the action as possible(usually on a roof top), ready to heal if necessary.