Your spec and gemming seem pretty acceptable.
Things I would change:
1) (and really not that big of a deal, some would argue it comes down to personal preference) swap the dodge/stam gem in your belt, the gem in your weapon, and the gem in your helm out for straight 30 stam gems, it will end up with more EHP.
2) I would also recommend you change your shield enchant to 18 stam since you are pretty far over 540, you can flex a lot of your defense easily.
3) I would also personally drop Ony's talisman for something like Glyph of Indominability if I couldn't pick up a brewfest trinket, heart of iron, royal seal of king llane, or a jug's vitality. And as far as easier to heal the raw armor from glyph of indom will go a long ways.
4) I'd also switch the Exalted SoH shoulder enchant to the 30 stam/15 resil shsoulder enchant.
5) switch glove enchant to 240 armor
But to be honest there's really nothing major or glaring, if I found you as a tank in my PuG I think I'd be pretty pleased. I think either the healers that are saying you are hard to heal are not doing their jobs right, or you aren't using cooldowns properly on fights (ex: shield walling impales on gormok). Warriors have to be pretty proactive with their cooldowns, so the more you can watch timers and anticipate, the better.
Edit: oh also, props for the 225 armor to cloak, for some reason a lot of tanks miss that... I did for a while =/