The secret to good tanking is to have full party awareness. It's a skill you'll develop, and I don't pretend to be the best tank ever, but basically you need to know your party inside and out. Is the healer great at last second saves? Don't bother holmganging. Is the DPS always jumping the gun and pulling first? Be ready for that and stand by your healer. Does your party suck at dodging AOEs? Position yourself so that it's easier for them to dodge.

And you have to know what everyone else is doing whilst also flawlessly performing your rotation, dodging every attack, and completing all mechanics flawlessly. Because as others have said, you're the first person to get blamed if it all goes wrong. But if some Dragoon is getting up in your grill, just remember that if he dies, the fight will just take longer, but if you die the fight is over.