Hmm I hesitate in case I ever pick up a PBEM game here at some point (because I wanted to see the surprise reaction to this bless tactic) but
LA Bogarus Khlysti
The pain transfer gets them through the arrows, but once one goes up the lack of Fire Res sends a whole clump up at once.
With Fire Res, they are more susceptible to individual casualties as they take ranged fire but are less likely to have a chain explosion.
I think long term once you get Fire Ward and whatnot it would be enough, but that's mid to late game.
I considered Air Shield but the goal is only to have them make contact with enemy toops before exploding, not actual survival. Plus my capital mages shoot fireballs and have the -prec from aging due to being octogenarians with fire path.
The nice thing about Bogarus is that it doesn't have to rely on the bless, but if you can make Khlysti deadly they are CHEAP and in non-capital fortresses. A hero slowly freespawns them too without taking an action, though because of their unrest increasing ability that's not so useful most of the time unless you taxi them away. It's great though if the Patriarch is part of your army and not just blood huntng / researching / preaching with his really high priest level. He summons more mad bombers every turn, so you'll generally have at least a handful.
EDIT: Figured it out
That's the Latus map from the Steam workshop. It's a Dom 3 map that was never finished, which is too bad. It's great for an all nations single player game.