And still negative procs today =/
The neg procs are from the 3.0 dot clicky, and it has always been like that, at least for me, since day 1 that the click was changed. although it says -2000 and such, im 99% sure it's doing positive damage. And yes it is for the click for sure because the numbers are rounded, since it starts at 250 and builds, where as the epic leech proc and buff proc and firestrikes all don't even in a nice even number (well except the epic lifetap but that is 6000 or higher)
If you want to test it to be sure, pull 1 mob and dot it, then just wait and watch the damage and see if the life goes up or down from a crit blast.