I challenge you to actually time it 10mins is a ridiculously small number and I'm sure even you can acquiesce that is an exaggeration. Remember that running time is not A -> B, it's A ->1 ->2 -> B where 1 and 2 where repositioning done while in battle (running to the next mob or moving around because you dont like where you are tanking/etc.) If you go to elitistjerks.com there is an actual calculation that shows how you cant get more dps from two talent points spent elsewhere than with the running speed enhancement. Now, of course, that is for a raid environment. I would hazard to guess that my time actually STANDING STILL(meleeing/dpsing in one spot) is around 20% of the time I am logged on (not counting afking in dalaran.) You can factor out riding/flying, but the point still stands. You move A LOT, far more than you realize. You can't, CANNOT, do a dungeon standing still and your guess of 10 mins is not realistic, at all.

edit: Just to prove a point I will run UK, Drak, and Gundrak from start to finish and time how long it takes to get to last boss(empty dungeon.) I am sure you will be surprised at the results. Now this doesnt take into account any of the repositioning that you will do countless times in a dungeon.