I've rarely seen these classes these days. Maybe their damage did fall off a bit further than expected. 

Reaper, as the class name suggests Reap, means she should have one of the highest damaging single hit skill.

I suggest buffing her Soul Reaver by increasing the range and AoE, amplify damage by 30% for every shard consumed, holding the skill button will consume 1 shard at a time, will attack after releasing the skill button or all shards are consumed. 

Sage, its class description says: 'channel infinite power and "instantly" warp space, causing "devastating" damage', but i don't think that's how he displays' his skills. 

I suggest buffing his Spatial Collapse a skill that sounds so catastrophic which should deal at least more damage than Yacha's Eagle Drop. Since Sage is considered as the slowest class, second to Drakania.