I think that Blood for Blood it only works on the first hit of any multi hit ws.

I saw a lot of times that my chaos was doing 80-90 the first one and 60-70 the other ones.

What i usually do on ifrit is B4B > Keen Flurry > Bloodbath > Doomspike, and when is down i do Chaos with no buffs. Thats less animation locks so less chances to get kill.