Archers have done the same thing with Rain of Death having such a short cooldown. Bards can shoot of Rain of Death so fast that their damage outpaces our DoT's as well with instant cast and a 2.5 sec recast. The only downside is the 200 TP cost. Oh wait there is a 15% chance that Rain of Death is free with the use of Wide Volley (another Instant AoE with instant cast, 2.5 sec recast and 160 TP cost). Once again, this is especially effective when they couple it with Raging Strikes with 60 seconds earlier earlier cast due Trait bonus.