It was only a 10% increase to OA in Ultimate, which is significant but certainly nowhere near a 2.5x increase. It was actually a bit less than 10% since they lost 3% to all attributes.
I inadvertently raised it more than it seems I should have while doing some rebalance to address issues with Elite.
In Normal difficulty mobs had -15% OA and received +10% OA in Veteran, with the result that they’d be at -5% OA. Elite and Ultimate were previously at -12% and -10% respectively.
So monsters actually lost OA going from Veteran to Elite… sort of an oversight on my part and part of the reason Elite didn’t feel like much of a difficulty increase.
To correct this, I set Elite to mirror Veteran, giving it -5% OA and then thought Ultimate should be a bit of a bump over Elite, so I set it to +0% OA.
In the process of editing the file, I’d forgotten that I actually started with -10% OA in Ultimate.
Based on feedback, it seems like innate OA scaling in enemies is really good enough by itself, such that there doesn’t need to be any bonus to enemy OA on higher difficulties. For the next hotfix, I’ve set all OA to -5% for Veteran, Elite and Ultimate, so that the only increase will be innate scaling, which seems good enough.
This will still be a 5% net gain for Ultimate over what it was originally but I feel that is probably reasonable. Builds with sufficient defensive investment that I tested did fine and I feel that if builds still struggle with that increase, they are maybe too skewed towards maxing DPS.
Btw, if anyone is wondering why normal starts out at -15%… it’s just how things ended up when it came to end of development balance turning. When it became apparently global things like OA, Dmg, etc, where over or under tuned across all enemies, the easiest thing to do was just adjust the global bonuses up or down, instead of individually editing dozens of enemies.