I use my flares if I pull aggro, once I got aggro I pop it. If everybody does their job correctly (including ourselves) we shouldn't be pulling aggro anyway. Just make sure you're not nuking something that the Tank only had a smash on. Always target the one that the Tank is slapping around unless he fails at doing his job and you need to get something off the healer.
Well I'm glad some people realise this!
This really bugs me when I'm on my healer and I see some random DPS guys just taking their pick of targets exactly the same time as when the tank rushes in -- no waiting for CC, no waiting for build-up of aggro. And inevitably, the DPS pulls aggro and puts pressure on everyone else. Very frustrating.
But I suppose we'd get bored of an easy life, huh?