I had this issue recently when doing a leveling roulette running DD. The healer in our group was very new, still had the green leaf (his gear was all over the place), but the Tank was decked out level 60 gear. The tank just ran through without a word and we wiped 4 times on regular mobs, not even the bosses. The healer just couldn't keep up, but the tank didn't really care, resulting in the dungeon taking far longer than what it needed to.

I understand that the dungeons are easy and often boring or whatever, but there are people who are just starting the game and don't understand the basic concepts of gear, or even being in a party with randoms.

I still think its important for tanks to at least consider the party make up, and making appropriate decisions about how to run dungeons before lunging through every mob like its a race.

And if all you ever want to do is speed run through every dungeon you come across, then do it with people who feel the same way as you.