Earlier today was solo'ing G.Coli's on 80DRG/RDM. My Wyvern was at max 'status parameter' increases but was healing for 2 different distinct numbers. Sometimes a regular HB would do about 480~ and other times it would do 571. Nothing in my gear changed. HB activated with AF1 Helm, and when HB goes out I have Wyrm Armet, Wyvern Mail, Gorget, Drachen Brais +1, and Homam Feet.
Also, just now I logged back in (so my wyvern as had no status parameter increases) and some HBs do 358, and some are doing 456.
I don't really understand what's happening. It's not a gear thing cause I changed my timers to be absuletly positive I had all my HB gear on when my wyvern hits me with it and it's still happening. It's not a Wyvern TP thing because I'm doing it so often that myvern doesn't have much time to build up TP before it's next HB...maybe 20-30tp. Does Healing Breath have some kind of Critical Hit type deal? lol.