I'll start recoding a few modules of the plugin in order to make Async viable. Currently if enabled i noticed there's a chance where it won't convert the damages and sometimes not block Velocity (sweep), I'll do some testing!
PS: Async is made to work on very low-end servers, Even tho it kind of seems useless since the whole plugin itself does not cause any lag at all. It's just there as a (Safe Mode)
Do not use it unless you're experiencing any lag (Very unlikely) Or until it gets Improvements