Passive Carrion Swarm - Base it off Critical Strike, set all values to 0.
Carrion Swarm - Original Carrion Swarm, make sure mana cost is 0, edit the values how you want.
Last Created Unit and Picked Unit don't leak. Groups does not need to be nulled, JASS stuff as mentioned above. I saw you posting quite a lot of times about null-ing groups and locations in previous threads which were GUI based triggers
Ghan has said he has fixed this. Monovertex please confirm this fix. This was only a problem with people that had signatures in the upper levels like not the special members but the respected members.