'A lot' of things if I to presume.
Damage result are not realtime anymore and as soon as its done outputting, it finalize instantly
Such as, you can see that now boss that suppose to be dead are instantly died once it's HP downed to 0 and no longer prolong its death by action timer just like it use to be.
Or most of the time, damage you dealt, no matter how big or small it'll not instantly dealt into boss's HP bar, instead, it's have a slightly delay before those number get input to the calculation and dealt them into boss's HP bar.
Which I highly suspect that they change some method for this calculation and outputting the final result, Are might be the major obstacle that Dwizpa came across, I do hope he notice that or this details on my pose.
What I curious most is, why must this kind of result are getting delay when it never used to be, maybe they change many things to depending on server side which might render us to be unable to mod those input via client side anymore, I just hope it's not.