Ladies and Gentlemen, Mr Buzz Killington.

Sadly he's right, threat issues should not be addressed by gemming for hit and expertise, working on your priorities and education of your dps are far more effective. You will probably need one gem not straight stam to make your meta, but everything else should be stam. Gemming for avoidance is just gambling with the RNG and you will lose.

The Glyph of Taunt is there because taunts use the spell hit cap, so even when you're capped for melee (with 8% melee hit), your taunts still have a chance to miss.

I would never advise a tank to reach for the spell hit cap.

At 253 rating he's almost capped already, so gemming def-stam in yellow slots is the most sensible choice if he wants a bonus.

Everyone is mentioning that Taunt is a spell and requires spell hit cap (correct), and that with 253 hit rating he shouldn't need glyph of taunt. 253 hit rating is around 8%, which is close to the 2H weapon melee hit cap. The spell hit cap is 17%. Seems there's still a bit of a gap there, and on a boss like Saurfang or Deathwhisper missed taunts are very annoying at best, and at worst can contribute to a wipe.

Plenty of reasons to gem for expertise and hit over avoidance stats. If you aren't at the 8% hit and 6% (I think that's what 26 converts to) expertise, then you're gimping your threat generation.

Be all that you can be, and all that. Once you hit the key threat generation points listed above, stack Stamina. If a socket bonus is less than +9 Stamina, ignore it and gem stamina. If the socket bonus isn't +Stamina, ignore it and gem stamina.

No stat gives better returns for a tank than Stamina right now. Avoidance is subject to the RNG (Random Number Generator). A bigger health pool is not.

It can. However in taunt swap fights it's also a good idea to vigilance your tanking partner for the automatic refresh on your taunt. If you miss then it'll be right back up.