The example I gave is an AOE scenario; there's no reason you wouldn't be able to Bane. There are two sets of Gusts, the first is a set of 3, and the latter is a Storm + 2 Gusts. In both cases the Gusts have to be tanked together. Even if they die in 10s, Bane is the most effective thing you can do. However, you're getting significantly less potency out of your DoTs if they die in 10s vs 20s. (And then waiting around doing nothing until next adds spawn...)

It's much less of an issue in a single add scenario like phase 1-2 Bennus, phase 2 Shadows, or in a multiple add scenario where you can't just kill everything freely like phase 3 Bennus (Well, depending on strategy).