Reaper needs additional buffs.

[ChaozK]

And yet monk has a better raid buff and mantra is simply better than arcane crest.

The amount of people trying to cling to the idea that arcane crest is good enough reason for reaper the "selfish" dps to be dead last is kinda funny.

Reaper is neither selfish nor is it dead last. Selfish means it gets to have high personal dps not rdps, which its currently at spot 3.
The only thing one can argue is that RPR should be dealing more personal dmg than MNK so it could switch to 2nd highest.

Arcane crest is also infinitely better than Mantra.