Reaper doesn't need buffs, the jobs are relatively close together in practical dps as most reapers do around the same damage. Some of the other jobs have a lot of variance in their damage by comparison. Like even if someone parses 10% on reaper on FFLogs, the difference between 10% and 50-60% on it compared to like, ninja, feels way lower. And FYI it is very rare to see a reaper parse that low to begin with unless it is a fight like P4S or maybe P3S.