Its fixed on ASR9900 through CSCwd70826.

Yes, PIM must be enable to route it. I don't have experience with this kind of design, but it should work unless there is some limitation. 

Have SVIs for VLAN A,B,C,D on a bottom switch (they'll pickup streams) & enable IGMP snooping only for VLAN D.

 Your Route Processor CPU (L3) traffic rate went down a lot, so its CPU load: kkmc-vss#sh proc cpu CPU utilization for five seconds: 15%/5%; one minute: 18%; five minutes: 18% kkmc-vss#show ibc brief Interface information: Interface IBC0/...

Well, it shouldn't go to CPU anyway. Can you check "show ip route 10.135.52.158 detail" @ kkmc-vss & routing for same destination on firewall. This happens often when traffic is coming out the same SVI (Vlan interface) as it came in.