There is 1 priest in the top 100'ish healers for Mogo Vaults Stone guards 10m.
And I believe that's holy. I checked disc earlier and the top disc parse was like rank 871 overall on that fight.
Disc was never about HPS or overall healing tho... I mean, I could be wrong, but the reason that R.Druids top heals is because they have 0 mitigation. Disc is *mainly* mitigation, so this makes sense...
I'd be less concerned with "rankings" (remember the days pre-absorbs in recount?) and more concerned with "unviable," which sounds like the issue. :/
I have 0 interest in learning how to play Holy, and will just lvl my R.Shammy as an alt again instead if Disc is not raid-viable. (My main will ALWAYS be my druid. :P) I came to this forum because very much want to play Disc in a raiding environment (mainly 10m normals, as we're a casual guild), and needed to see if this was possible in MOP... But doesn't sound plausible at this moment? :(