ive never gotten over a 9.5 crit heal with ancient yet, except 1 time with earring aura going, 9998 crits ><, cant remember any 10k heals while a pally clicked his aura, but coulda been RNG luck or wasnt paying attention to them. had alot bigger heals with pally epic clicks (28k before they nerfed it a long long time ago).
the kicker is that we wear a ton of healing focus that our heals can hit anywhere from 3300-9500, and RNG for the focus and crit whill come into play alot. theres huge difference in our healing potential because of the focus