OT on patch is just an example, amybe not so sharp because of damage being only physical. But lets take Malygos or Sartharion 3D, there is no way paladin or warrior can be as good MT on those encounters as druid or DK, just by design. And Ghostcrawler admits that it is ok. Tank equality my @#$.
If devs think that blocking for twice as much sometimes makes up for not blocking at all sometimes, as long as overall damage taken is equal they are wrong - spikes kill tanks, not the 3% difference in damage taken seen in wws... In TBC palas and warriors were non spike tanks, since we didn't get crushed, unless very unlucky or lazy. Now paladins kept this quality, but warriors became tanks with spikiest damage of them all. So what that I am blocking 15 - 30% of teh time, if healers have to heal me anyway like I will not block at all.I find block itself to be a good stat. Even rating is good if you aren't block capped yet. Yes, for a warrior it is typically less reliable because you can no longer guarantee a block, but it isn't like block stops working the moment shield block is down. There aren't simply two extremes where on one side shield block is up and you are blocking attacks and on the other side shield block is down and you no longer block. You still should be blocking 20-30% of the time, which while not as good as avoidance, is still decent mitigation. I am not sure I would gear for it specifically (maybe an experienced warrior can comment on that), but I definitely wouldn't discount it as nothing. All of our forms of mitigation (and avoidance) work together to keep us alive as a whole. Just because a contribution is small doesn't mean it is meaningless.
If I had to guess, I would guess that warriors are balanced around the fact that they don't block all the time and that it is random when shield block is down. Of course none of us are blizzard devs, so that would be only a guess for any of us.
Its my threat set.EDIT: As a note, I noticed the OP was gemming for hit/expertise. Those are definitely important threat stats, but if you are having trouble with survivability, then you might consider gemming for avoidance instead until you feel comfortable going back to hit/expertise.