which one is better?

due the skill calc:
Devine Healing (at max):
restores 1120 LP
9sec CD

Kamis Mercy (at max):
restores 2468 LP
17sec CD
1sec cast time

but with kamis healing technique its more than 1120/2468 LP what u restore.

so whtas better?

and with a lvl 60 staff +10 how much do u heal with both skills?

I maxed healing wave (3sec CD) so i can heal almost all the time..

divine healing is waay better lower cd so you can spam it and no cast time
cast time can be anoying when you dont have the fastest internet conection or the best pc cause it can go from 1 sec to 2 or even 3 seconds and then there is the cd
but it you are going for full support max them both