People are used to tanks who pad their HP above the gear level they are at.
I even do it.
I have ~30k hp, but I'm less geared than you are.
You have plenty of avoidance and mitigation, your HP isn't too low, and you have the threat stats you need.
It's a trend that people want 'easy' mode tanking. Warriors have probably the lowest HP totals when compared to the other tanks, we have fewer means of boosting a % of stamina via talents, etc...
So to say you have low HP, is correct, you don't have complete set of top end chants and gems. You could probably get to 32k in your current gear set. It really sucks that people are looking a single stat when regarding if someone can tank something or not. HP is very important, but it by far isn't the only stat that matters. Their are groups of people out their that are getting 'elitism' anger out by telling you that your low on HP. Your not. Your also not a MT for a progression guild for hard mode coliseum, where you'd have ~40k+ hp.
To give some comparison, before Ulduar, nax25 geared tanks had ~35k hp. They started with ~28k hp, for nax10. You have as good of gear as nax10 ilvl. You have a few pieces of very nice gear, and honestly, you should just sign up for a pug raid and try to tank. Getting into a guild may not be enough, people are getting pampered with progression raid tanks for heroics, and it's that kind of mentality that makes the game not fun.
List of specific things;
Shoulder Enchant (your on it already)
Cloak Enchant Bracer Enchant Socket Belt Better Boot Enchant Weapon Enchant