This brings up some things I had been wondering about. You already answered one question which is whether ERA can get blown off in the first place.
The other is how is ERA expenditure simulated? Does any hit just blow one brick off, or can I say, knock all of it off the entire side of a tank with a single large HE round? Also, would repeated hits from Mk 19 HEDP rounds knock off a lot of it? I remember one of those T-62s in this scenario taking a lot of HEDP from one of my AAV's, and rather than fight back, it backed up to get out of LOS. Probably had busted optics