Yeah, CT is good to the point where for AoE fights (Wind-lord) mastery's value is greatly increased.
Yeah when MoP released CT was better than Eviscerate single target. That was fixed early on though, now its about half as good.
I have selected the 5% all stats buff - so it'll get the bonus from that. Turning it off moves it back on par with AP.
Yep, silly us. On the note of enchants, I'd just go with haste or something since even if Str is your best stat it soon won't be and haste is mad cheap. Plus if you are using another spec then str will be useless. Are you sure you aren't set to Assassination? That spec values AP a lot higher and thus Str is right under mastery, it's best secondary that isn't hit.
PvP bonuses are all useless for PvE so no reason to get sets for them.