I use MSBT but i don't use that glyph. I've not seen anything like that, but i do see "6 hits 1 crit" with it quite often, but i'm gonna go check it out.
Here's what i got;
This was on the level 60 dummies in Orgrimmar since they're the most grouped. So we've got HotR hitting 3 targets, and it seems to chain SoComm to 6 targets, which indicated that the target that HotR hits isn't hit with a SoComm proc, but the other targets are infact hit by it. It also seems to be able to chain back on targets that HotR hit, and i also noticed it hit the dummy that HotR didn't hit.
I currently use
Hellscream Slicer from Anub-25 as my threat weapon, simply because it takes my damage range to 1124-1463 self-buffed as opposed to sub-1K top end with other weapons.
I tested with Thunderfury, and unfortunately, the proc from that doesn't proc SoComm (shame since that'd be another 6-8 procs). However, it DOES proc from ShoR and Judgement, but not AS or Exo or HoR.
However, the results are there that SoComm is fairly formidable. Had SoComm been this way in TBC, it would have been legendary for Hyjal. You need to remember that each procs can crit, and in ICC trash, i usually see at least one per chain, and more when i use HotR.