I didn't want to necro any old threads, since it would just get locked, so I'm mentioning it here. I tried the Overload ultimate today and it appears to be working fine now. It was mentioned in the patch notes for update 37, so I thought I'd check it.
Patch notes text:
Overload: Fixed an issue where this Ultimate and its morphs would not remove themselves when Heavy Attacking with just enough Ultimate for 1 tick.
PC(Steam) / EU / play from Melbourne, Australia / avg ping 390