Sorry to hear you are having such trouble. We use a fair amount of multicast applications, and have never had issues with dropped packets. We don't have the vm density on our hosts to require splitRxMode, the default config has been fine so far. Only multicast issue I can remember is the spam caused by multi nic vmotions running longer than your mac table timouts, but that was fixed some time ago.
Just to be clear, is the VM in question the target of the multicast or one of the recipients?
You only mention the one server, a rather old dell 2950. Have you tried moving the VM in question to more modern hardware? Can't really complain ESXi isn't ready for mission critical applications when your running it on a server model Dell won't even warranty anymore 
Sorry, bad joke, but there is no way for me to do that research, as Dell servers are warrantied for a max of 5 years from date shipped from the factory, so I would need to know when you bought it to be sure it's not past that. All of ours went out last year. If you have warranty coverage through the end of 2014 you must have bought the last one
My post was more to state that we aren't seeing the issues you are, so it may be a combination of variables in your particular environment than a general bug in ESXi's networking, but you probably already gathered that from the blog post.
I'm not sure why you would assume that because your experiencing an issue in your environment everyone else is as well. We don't have multicast packet loss, or any other type of packet loss, beyond what you would normally see for link congestion or other normal packet drop situations, unless we are dealing with faulty hardware or cabling. Andy yes, our NOC and network engineers know how to use packet sniffers. We are a financial institution, and we run many of those applications your referring to, and are pretty sensitive to our applications not working as expected.
Without knowing what steps support has already had you try, it's hard to suggest what else to do. Moving the vm to another hardware combination is a quick way to rule out firmware and nic driver issues, etc. Depending on how much effort you want to continue to put into chasing the issue vs reverting to a dedicated physical, you could replace VMware's generic DVS with the Nexus 1000v and see if it exhibits the same behavior. This would also give you more visibility to track the packet activity inside the virtual switch.
I have to say that I too also have this multicast issue and it VM TAC engineers are not very helpful either. TAC engineers confirm that the VM distributed switch is not passing multicast traffics.
After multiple attempts with upgrading to the latest patches and fixes by VM, the issue is still there. We're running ESXi 5.1 update 2 with latest patches with latest BiOS and firmware on the Dell R720
Long story shorts, we replaced these VM Servers with physical servers and no more multicast packet drops .
VM is nothing but trouble.