It seems like Blessing only works if another Priest casts it on them.
Even if you’d be able to buff your zombies on your own, Blessing still has target limit though so you can’t buff all 20 Zombies at once!
Someone discussed about buffs Zombies can receive here: https://www.reddit.com/r/treeofsavior/comments/4atn9u/bokor_zombies_buffs/
Also, it’s not like 78 Strenght from Divine Stigma is gonna make them hit like trucks 
The most useful among the list there I think they’d be:
- Revive
- Aukuras
- Zalciai
- Increased Magic Defense
About Revive, anyway, it probably doesn’t even work anymore. I have read some other posts about people using the Revive+Damballa combo but zombies do die now instead of being able to Damballa more times…
As for Stone Skin, I have read they do get the buff but they won’t ever block. Same probably goes for Quicken/Haste, although they do get the buff it doesn’t seem to be 100% effective (I once had a friend do it to my zombies and I couldn’t notice much difference…).
I’m also trying to build a total “Zombie Bokor” build, where the character only works as a “support” to them. So far, only Cleric2>Bokor3 is the safe route if you’re going for that.
I make that on full SPR build to also have them be more tanky while making them deal damage through Deprotected Zone + Zalciai.
I just started another thread seeking new synergies for our Zombies, so far I found out “Taoist’s Fade” won’t affect them while “Taoist’s Storm” for +50% Physical Damage might work a little, but 7 seconds only seem not to be the greatest thing to raise Zombie’s DPS, I’m still waiting for someone to share his knowledge about Inquisitor 
You can give a look here: Questions about Inquisitor's Skills and Zombie Bokor Synergy
If even Inquisitor won’t work, I guess the path would be more likely Cleric3>Bokor3>Miko>Pardoner then waiting for R9 classes, I’m pretty sure either Macumbeiro or Shepher will have synergy with our pretty little creatures 