Don't let a few bad apples ruin your tanking experience. For every one of them, there are hundreds more that will help you out! I love tanking, and generally, rarely deal with those types of people. My main antagonist are Bards. For some reason, Bards always think they should tell me how to tank, what to do, etc. It's funny in a way, especially when they don't have a tanking class themselves. You gotta run it your way, you are leading the party. Without you, especially on duty bosses, they won't last long.

If a DPS pulls ahead of me, I'll watch that critter run by, and maul the DPS. I'll pull aggro on other creatures, and let the DPS deal with it. If they wanna tank, I give them the chance. All in all, I've met so many great DPS though, those few stick out like a sore thumb. Keep at it, I am sure you'll do just fine.