Honestly, this fight has me baffled as to what works best. Not only do I not know which tactics to use, but my attention is called to so many different things (CC, Debuffing, avoidance tactics, a bunch of adds to DoT), that it's hard to even think too much about DPS. Either way - it only took us 2 real attempts to kill it. So I can't complain. But perhaps with some more attempts I can try some different tactics.
Did you use FDCL when you weren't using mindseer? What was the filler?
edit; literally just did lfr and got rank4 testing without any mind sear - beat my previous dps by about 20k.
now i'm confused.
I'd say it's because rolling DoTs is more effective DPS than Mind Searing. Blue posts going back prior to 5.0 indicated the dev's intentions behind nerfing Mind Sear were to make SPriest AE DPS more than just spamming one button. Granted, with the 5.1 buff, Mind Sear on this fight may be more effective DPS than multi DoTing; but at the moment, if you can maintain a high DoT uptime on all of the targets, multi-DoTing edges out Mind Sear by a decent enough margin to make it the better DPS choice. The margin between the two methods seems to vary from Priest to Priest though, so it really boils down to personal preference. I don't like Mind Sear spamming myself (Yor'shaj flashbacks), so I prefer the latter method.