might be good to make AI civs declare war on their enemy civs (especially when Raging barbs is checked, since an AI in war mode survives the raging barbs easily)
we've played tons of Always War/Raging barb games with my modmod, and in it i removed the barb bonuses to the AI, and found that before we meet the AIs they sometimes die, but after we meet them they dominate the barbs. the reason for this is because before we meet them the Always War option doesn't come into effect, so they have no wars and are in peace mode, despite being in a dangerous condition (i.e. barbs mass attacking), but after we meet them, the AIs declare war automatically and then theyre in war mode. having some minor wars always going on would help the AI to survive the barbs and benefit from them the way players do (in our games the AIs get tons of xp like a player does, because they build tons of units and fight a lot of winning fights against the barbs).