AM's deserve some sympathy here imho.
It's not "meta-chasing" if you're bummed about your build suddenly dealing 59% less dmg. Absolute endgame AM's are probably still relatively okay, but players that were just able to hit necessary dps milestones to farm certain places have taken quite a hit.
There's a reason many games usually try to bring weak classes up, instead of dragging strong classes down, it just feels better for everyone.
But of course, this is different. It's not a concious rebalancing, it's fixing a bug, and I won't argue that it was necessary.
I also wouldn't go as far and say that AM players are necessarily entitled to compensation, but I agree that it would be a great sign of good will.
The main issue I see is that it would probably take quite some effort to build a specific reroll system that will be disabled again after some grace period. I don't know if it's more feasible for GMs to update it in the database just once for people that sign up for it via ticket or similar, but I could imagine that it's still a bit bothersome to deal with from their side.