if you're #1 on any fight but elegon you need to replace your other dps.
priests are okay, but warlocks are way stronger at everything we have (even their raid heals via healthstone are better than anything we have in shadow). unless they come up with some very good set bonuses, i can see shadow being in very tough shape in later tiers. we have zero burst, and our multidotting is waaaaay too slow compared to warlocks.
They can be singular, there's a huge debate on the merits or otherwise of it here... http://en.wikipedia.org/wiki/Singular_they