That '84 tone is pretty illusive and definitive. One thought I've had about that time period and tone is that this was Jerry often at his loudest ever (and wasted). That crystalline, sparkly grit sounds to me like the ultimate example of a maxed Mc2300 and stressed out JBL's.
I also still have a theory, and it's completely just a guess/theory. There's something about those couple of years, '84 and '85, I could swear I hear quite a bit of hard limiting on things, namely Jerry's guitar so that everything he played, soft and clean or hard and dirty, it all was just pushed to the front. I've had board tapes of those years since the mid 80's and I always noticed that Jerry's guitar sounded squashed, compressed. I know Healy wasn't into compression, but he was very into using peak limiters. I just wonder if we're hearing some of that limiter smack added to the sound of Jerry just burning thru JBL's and abusing the Mac in a big way. I seems that by '86, '87, it sounded more dynamic again. Anyone ever notice this about the '84-'85 stuff?