yeah, Mokka doesn't do much, but when he does, it's bad. Really bad. I had have him attack me early once (Illians built Samhain from start) and he becomes a powerhouse after a few combats. Though he stopped short of taking my only city, he gained combat 5 and laid waste to the Hippus. I'm not going to complain about that one though 
I've never really seen frostling archers attack, but those wolf riders are pesky, to say the least.
I think, the frostlings uselessness depends on who's the barbarians current target. I've often seen a civ wiped out after Samhain is completed, so it's far from useless though.
I've also noticed that all barbarians, not just frostings, occasionally just fortify on a tile indefinitely. Even if they could pillage or try to sack a city. Anyone else notice this? It usually seems to happen with goblins and archers.

I've never really seen frostling archers attack, but those wolf riders are pesky, to say the least.
I think, the frostlings uselessness depends on who's the barbarians current target. I've often seen a civ wiped out after Samhain is completed, so it's far from useless though.
I've also noticed that all barbarians, not just frostings, occasionally just fortify on a tile indefinitely. Even if they could pillage or try to sack a city. Anyone else notice this? It usually seems to happen with goblins and archers.