Now as Holy I would definitely go for the 4 set and drop the legs for Heroic Stone Guard legs.
However as Disc, I don't really see the point. 4 seconds off penance? I'm considering going for the chest and gloves with crit on them, instead of the tier pieces with haste (gloves don't even have a socket either). I'd still get 2 set just because the shoulders and helm are spirit + mastery, but that seems pretty useless as well.