I think this change is harsher than any of the other changes. I understand that casters didn't exactly have a chance before, but now we have a problem where it is very difficult to kill through all of the uninterrupted heals. Culling Time has gone from a passive-play countermeasure to a necessity to get a kill in many situations, even in 4 v 4 matches.

As a tank I feel useless outside of the 10-20 second window where I can set-up a kill with Full Swing, and Holmgang + Brutal Swing or Shield Bash. Most casters now simply ignore me as my attacks are not bursty enough to consistently interrupt their casting.

I would suggest changing it to either the same system but with diminishing returns (lower HP% while they are being attacked consistently) or something like WoW's system where being attacked while casting just sets back your cast bar a little bit, effectively slowing cast speeds but not stopping them outright.