1. gearscore does not equal skill. yes those other hunters might be in better gear but they could be complete noobs with rotations and not execute them properly. mm and surv will both beat bm given same gear and skill. mm stomps the other 2 specs in bis gear and equal skill.
2. since most of your dps comes from your pet, you don't suffer as big of a penalty as the other 2 hunter specs when dpsing on the move, which many fights in icc involve.
3. those other hunters could have been clickers.
4. improper cd usage compared to yours.
again, given equal skill/gear mm will beat surv and bm, while surv is comparable to mm at lower gear levels where mm can't get arp capped. both will beat bm at most all gear levels (leveling and fresh 80 bm is viable).