On Retadins....

Feral Druids can OT w/o respeccing.
Arms Warriors can OT w/o respeccing.
Ret Pallies cannot OT, period.

Holy Shield is too deep into Prot, and w/o Holy Shield, you just can't tank effectively -- and that deep into Prot prevents you from getting Crusader Strike, your bread and butter instant ret attack.

If you want a silence-immune tank, you want a druid, as they can still multitank, unlike wars which rely on micromanagement.

And yeah, if you're 10-boxing, just say no to CC. That will never happen reliably.