The lowest damage cast I’ve seen so far is 70 on the first target, so approx 175 total damage. YMMV. I think my base is 30 so that’s 5 boosts.
EDIT: I originally thought the boost ratio applied to stacks of bleed, so it would be possible theoretically to have 20 boosts. But I guess max boosts is 8 if it doesn’t count stacks, just bleeding “enemies”? This does cap the damage ceiling much much lower.
Maybe even just several months ago, before we had so many 10-star kingdoms with extra stat boosts, and fewer factions available giving renown stat boats, and before pets could give 2 levels of stat boosts. It can add up to a lot of extra life and armor now, one full year ago it could have been brutal! Then again Bleed didn’t exist a year ago either so you’d only get half the boost 
EDIT: reminded me of this thread of fire giant losing 1-shot power thanks to new life/armor kingdoms, magic is slow to increase compared to other stats Let's add Magic to the list of things to review