On fights where people are stacked I use healing rain plus conductivity. Conductivity can be seen as a mana saving talent but actually, every healing rain you don't have to recast is an extra chain heal you can keep on spamming. (Roughly). I have found this to provide more healing than the extra heal on hst if enough people are stacked in it consistently. If it is a fight where we move slightly like Oreo (depending on your groups strat I suppose) or imperator or tectus, I try to place it so that we can remain in it longer. Though Oreo is potentially i fight I would drop it for. I would agree