EDIT:
An idea is at least reducing the duration of the chests, because with a Pride and BM 300 buff with a zBrew the duration is way too long
That certainly is a solution but it is very focused to one part of the game - GVG( more specifically if you only have one target and they used egg or if all target members used egg) so it would affect other aspects of game and affects its value of such a rare potion.
If I could suggest, changed the way DC works to UB. Even when you have 230 UB you will take some damage and I don't have a source but even if you are at 230, it has a hard cap at 94-98% percent. Now the percentage would have to be discussed or at the discretion of HCS but that way it wouldn't be a guaranteed buff