Perhaps à good start would be to either reduce its cd or make its radius weider.

Or another option would be to make it heal twice for half duration do people wouldn't have to stand in it for so long.

It could also have a lengthier duration but smaller potency (doubled with the huge radius) having a nearly permanent hot could be interesting.

It is true CI is currently better, but I don't think it needs a big tweak to become a good skill. The fact that we can step in and out could be exploited and become the ability strength