I got started last night ... so far I must say that Flare is going to be extremely familiar tactics-wise to players that practiced clearing rooms in ME1. The sheer damage and radius is comparable to what you got from using overload/sabotage on fuel canisters or using certain wide-area biotic powers, so it's best to use it like a grenade - flip it off at the very start into a packed bunch of adversaries, possibly with a power of your own to add a combo explosion, and then mop up the horribly maimed survivors with gunfire. As far as incorporating it later as a bonus power, I'd say the one that would really benefit from it might be an adept. The long cooldown time is counterproductive to a vanguard's tactics and the cooldown penalty on tech armor could make it horribly slow for a sentinel. However, an adept with a very fast cooldown time might well turn into an explosion-spamming nightmare - Jack's concept of "biotic artillery" in action. Of course, you might say the same for an engineer, but in general I like to restrict biotic powers to biotic classes.