Niantic have made mistakes, but a 50% buff is ridiculous. You aren't giving them enough credit here.
All T3's SHOULD remain soloable, though some will be harder than others.
MOST T4's should not be soloable, but I suspect that finding a real squishy T4 boss could still result in a soloable raid.
I think the real goal here was to make it so that Deoxys A is no longer soloable. Why bother making EX raids a big thing when your raid boss is as frail and easy to beat as a weedle? The solution: Make bosses tougher, but you don't need to go overboard with it. Just make Deoxys A a duo raid minimum, and then when Deoxys D comes out youll need to 6 man him.