If you don't see threat as an issue, then I would take their advice and switch to a spec that is geared more towards survivability. I'm sure you already know this, but the deep wounds spec helps with threat on larger mobs, especially on heroics. Now that you are tanking the higher end raids, a survivability spec might make the difference. I noticed your expertise is a little low, and you may want to get that capped to help your threat and make it easier to switch to a survivability spec.
Also, it could be attributed to class mechanics. I don't know all the stats, but I've noticed, at least compared to pallies, warrior tanks will take more damage. The other warriors could be using their cooldowns more effectively, which can really help negate damage ie., Shield block.
Your gear isn't bad at all, and it looks like you are gemming for full stamina, which is a good choice.
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