Never tried Dark setup with Weiss so I'm not sure.
The damage gain is minimal, you can absolutely ignore it for now for the easier version. Just do stuff > 6HC > 2A 5B 5C [sjc] j.A j.B j.4B [jc] j.C(2) j.E
As for tips on getting it down, just homing j.C as quickly as possible after you jump cancel the j.B - it's gotta be fast. Also you only have to whiff the j.E from certain heights, normally you can ignore it and still land in time to 5B. Not having to worry about that should help you concentrate on the other things you have to press.