The tooltip reads that any damage taken will trigger the heal. When I have shield block up, unless the mob on me casts spells, I do not get the Blood Craze buff, even though I am still taking damage when I block an attack.
Not only is it's up time terrible, but it can proc while it is still up, also hurting it's total uptime. In the latest beta patch, it was reduced to 3% of total health over 5 seconds, costing 3 talent points.
With Field Dressing, that is increased to 3.6% maximum health over 5 seconds.
Comparatively, druid Leader of the Pack heals for 4% of max health with an internal cooldown of 6 seconds costing 1 talent point. Considering the high crit chance of druids, I think it would be safe to assume a proc every 8 seconds or so.
Assuming 150,000 HP in Cataclysm, the druid talent will heal 6000 health per proc. At 8 seconds between, it will proc 7.5 times per minute, for a total of 45,000 healing.
If the stars aligned and Blood Craze was up immediately after it went down, it would be up 12 times in a minute. At 3.6% health per proc, it will heal 64,800 HP.
In it's current state though, I only see it proc 3-4 times per minute because of only having a 20% or so chance of actually being hit. If a boss swings once every 2 seconds, that's a possible 30 hits in a minute. 20% chance of being hit reduces it to 6 chances to proc Blood Craze per minute. At a 10% proc rate, that is 0.6 swings per minute that proc Blood Craze.
Sure, in actuality the proc rate slightly higher because of boss abilities and spells. But 3-4 procs per minute is still only 16,200-21,600 healing over that minute.
If damage taken through a block could proc Blood Craze, I would be able to have a chance to proc it from 60% of swings, giving me 18 chances to proc in a minute, and 1.8 ppm from auto attack hits. Still not very much, but better.
I understand that balancing these things is difficult, there's a huge difference in number of procs during AE pulls and boss pulls, whereas if the player's hits can proc the heal, there's slightly less of a difference. I hope something can be resolved to have warriors catch up a little in PvE self healing.
Edit: A wrong number