Like Machetazzo said, the key is anticipation. Stocking up on Aetherflow stacks to Bane --> Fester, also don't forget about Energy Drain, in a pinch you can output some nice burst, especially if you have 6 stacks waiting in anticipation. Sometimes if things get desperate (kill it or wipe) I will use Enkindle.

Also don't forget about Rouse + Spur. You can save those for burst as well (but never hold on to things past their cd, i.e. holding onto Rouse for over a minute).