Yeah, but it's gonna cost me another enhancement unslotter to get the proc out of Stamina so the FP one is the only one I have... gosh-darnit...
As you can see, it hit me for 68.16 endurance off this one Hellion. My maximum endurance is 113.6, so that's six times the 11.36 endurance it should be giving me. Looking at this now, having slept, it's obvious to me that this is because the effect is scaling off the level of the enemy affected, which I verified by trying it on some level 54s and seeing it give me 7.38 endurance.
I also found another bug getting this screenshot: while Ice Patch is up, you'll get that "You freeze the ground underneath you into an Ice Patch!" every time your character lands on the ground, whether from a jump or from falling off of something. Probably related to this other bug I reported regarding Ice Patch.