I'd like to add my input as a level 25 cleric.
I think heal is absolutely fine as it is, though some kind of scaling may be appropriate, but it would have to be a very small change or OP.
The biggest benefit to clerics is how long they last. At level 16+ I could easily complete crypt with no pots and 2 full heals, and at 23+ without full healing at all. With the right build, it's really a simple playstyle class that has a bit of everything. The biggest skill is intervention, just crazy strong (by far the strongest skill in the game) and for only 1/1/1 I have always felt this to be far too OP for the cost.
I would adjust things slightly - increase intervention to 1/2/3 or 1/2/2. Change heal to 1//2/2. This adds more interaction in playstyle. Change crusader to 1/2/2 and barrier to 1/1/1. If you count the skill point changes, it is actually the same as before, but encourages more active play. Currently intervention is way better than heal which seems wrong at a conceptual level.
I would also add another advanced skill on par with flurry, though I remember you said it is in the works. You can make it an open skill with requirement 6 personality.