Extensive testing in Phase 3 had MNK with the highest DPS ceiling by a significant margin. Given Paeon from a BRD, this can hold true for extended battles just as readily.

That being said, some tweaks definitely were made, so looking forward to checking out the details after Launch. With the differences measured in Phase 3 in mind, and a quick look at some of the tweaks to both actions and damage calculations that I could tell from Phase 4 (like DoTs being affected by buffs now) I feel that all of the DPS being much closer to each other is a good hypothesis.