I have had a look at the patch notes for v1.52 and I found this:
Is this still true on phoenix?
In RvR only, area effect Mesmerization spells have been modified so that the duration effect of the mez spell is lessened the farther the player is from the center of the area of effect. The duration is 100% at the middle of the area, and it tails off to 50% duration at the edges. This does NOT change the way area effect spells work against monsters, only realm enemies (i.e. enemy players and enemy realm guards).
Is this still true on phoenix?