While you're right with almost everything you said and since there is a major flaw with simcraft. Which is multiple targets, movement, phase changes, etc. It's a bit more complicated than that.
An affliction locks single target dps is 12% higher than ret, but if you add more targets EVEN with movement that drastically increases the gap between the two specs. So on patchwerk fights and anything with adds the aff lock is significantly better. Now on the flip side you have burst phases with vulnerability phases as a mechanic. Well this is almost certaintly going to be the minority but you can be assured that while the paladin will perform much better on that encounter type over any other it will most likely not be enough to have it swing in the rets favor by 12%. So overall we know locks are better, not to mention they have other specs for burst to minimize the difference there. Also warriors as well as rogues are better.
Nowadays with 10man raiding being the norm and dps slots limited it makes little sense to take a dedicated ret. Now while you can still say "get friends or join a guild" and you'd be right.. that doesn't change the fact I could pug on my alt lock, warrior or rogue much easier.
Now this isn't going to stop me from playing ret but the cause for concern is there same thing on the PvP front. It's viable IF you are an above average player that know people willing to accept something that could be filled better with YOU playing a different class. Good luck convincing a pug or meeting new people that are decent in accepting you as a ret.
It's not like you couldn't look yourself in the mirror and say - If I was a warrior/rogue/lock/mage instead of ret my experience in finding pub runs and rbgs would be significantly better. What if they are a new player trying to prove themselves, forget about it!