I am interested in Sephice's answer as well.

but while strategy/tatics does make a big difference, I think it falls more onto the battle field awareness and reaction time. In other words, skill.

It doesn't take much to realize the way we played 4 melee zergs is not viable for 2200+. Zerg 1 healer while leaving the other free and letting the rest of the dps peel off your slaves is simply not going to work. Any teams that understand and execute the concept of "peeling off" will beat us.

Rather than focus fire one of the DK right off the bat, simply start the game with 1v1v1v1v1v1 CC to completely neturalize our team. Then focus fire 1 DK to win.

The way I see it, 2 ways in playing arena

1. force the issue
2. see or predict what's coming, then counter.

and do it with super fast reaction.