The difference between a Moebius Sin and a non-Moebius Sin:
Sustained DPS pressure.
Without Moebius there's no real incentive for you to stay in combat. Short of buying a Tome for it, I suggest shifting your focus to the more 'traditional' Sin task eg spiking down key targets one after another. We're thinking Shadow Steps combined with heavier spike damage here - preferably with a built-in way out.
If you've reached Kaineng already it's but a short run to Xuekao... from which Assassin's Promise can be capped. AP is widely considered to be the 2nd-most powerful PvE Sin Elite after Moebius, and allows for gratuitous use of powerful attacks like Twisting Fangs - the recharge of it would otherwise be a significant downside in PvE.
Go get 'em.