My go to combo, starting from 3 stacks of Aetherflow, is:

Virus > Raging Strikes > Bio II > Miasma > Bio > Fester > Thunder > Contagion > Energy Drain > Ruin II > Fester

That gives you maximum single target damage possible.

For groups I always use:

Precast Shadow Flare > Bio II > Miasma > Bio > Miasma II (driveby) > Contagion > Bane > Fester Mob#1 > Thunder on #2 and #3 > Spam Ruin on #2 and #3 > Recast Miasma II when its about to run out.

Seems to tear everything a new butthole.