I play ret in M+ as 442ilvl, i've done my fair shares of 12-17 keys and i can tell you the bad bad stuff about the spec (and the good)
Most of their utility is only useful in a small amount of circumstances, they were ok last week with necrotic and bursting because WoG and bop can be very handy, other than that it has almost no use other than saving yourself.
they have no good CC for dungeons, so no aoe stuns unless they are undead/demon, if they choose blinding light it has a fucking 2 min cd.
Now the damage, single target, yea they're decent i'm almost always on top on bosses, but M+ is all about the trash, Rets AOE during wings can obliterate packs with the right traits, but outside of it you can often be very low on dps unless you get lucky with divine purpose/emp power procs, at higher keys you need high consistent dps on all packs.
but overall the utility of other melee just outshines us (except dps warrior)