Collective Unconscious

[Rongway]

I didn't realise the HoT continued after cancelling the ability

It does, and as long as you're channeling, it refreshes the duration to 15 sec on everyone inside when it ticks. So if the boss has disappeared and there's still, for example, 12 seconds before a big AoE, you can start channeling, give everyone 12 sec of super regen, reduce the damage from the hit, and then still have another 12-15 seconds of super regen after you break your channel.