Xp didn't increase last cap. It was 100590xp for 61, as it is for 66. Xp for 56 was 83840xp, but there were no 4x xp elix at that time, and 1 hour elix didn't exist.
So yeah, personally, I'd say 100590xp on 4x would be fairly similar as 83840xp on 3x, give or take a few xp, wouldn't you agree?
Bookmarks