I can only tell you I've tried the snooping when the controller wasn't the VLAN router, and it worked fine. If it was the router, can't see why it would not work, but I might be wrong.
You're right, no PIM.
You mention mDNS, is Airgroup not an option for you?
"it appears that without an IGMP querier in place, the IGMP snooping on the Aruba is not working reliably (no memberships in the Aruba IGMP groups.) If I turn off IGMP snooping, the mcast traffic makes it through, but I'm afraid it's just being flooding."
It sounds to me like the stream source is off-net, and the snooping is blocking the join before the querier hears it. So, in that case, the other comment about proxy sounds like an option. Either that, or perhaps try putting an IP on the controller in the same VLAN as the source (which might not work if snooping was on the switches in that VLAN).
With snooping and proxy off, it might well flood. You definately want to drop bcast/mcast in the VAP. Also, have a look at dynamic mcast optimization.
Thanks.