To begin with, I'm a part of a "casual guild" - we don't raid every week (tho we try to), we sometimes need to pug a player, or pick an undergeared guildie. We are no pros, thats for sure. But we constatntly try to progress through MV.
Back to the topic. Stone Guard needs nerfing - and fast. I'm talking about one aspect of the fight - Jasper Chains. This skill is WAY harder to deal with than the rest of them, with Jade and Amethyst being trivial, and Cobalt only slightly harder. Jasper+Cobalt combo is a progress stopper. If this combo occurs, the very 1st boss you face in MV is harder than both Feng and Gara'jal, and most likely Spirit Kings - had only like 2 tries on those, don't really know.
Blizzard should do something about this, with Jasper damage lowered by a large amount or only 1 chain existing at the time. It's kinda sad when our guild, thinking about nest weeks raid, rather thinks how to get past Jasper/Cobalt/Amethyst combo then about last encounters.
And just for statistics - we had around 10 wipes on Feng and 10 wipes on Gara'jal before we downed them, and over 60 before we downed Stone Guard for the 1st time. And it was pure luck.