Tanks are require to pull x% mwithing x minutes of time. This usally means you have to AT LEAST double pull most packs, and oftentimes if lust is going to be used on adds you triple/quad pull.
IF you are unable to keep up thats a YOU problem and you need practice. Full stop. If the tank doesnt pull in the manner listed above then DPS are unable to hit their numbers (Most packs are 5 mobs or less and most aoe is softcapped at 8+) and the group will be unable to time. Again if you cant keep up you need more practice. Tank can quad pull (regardless of my role) and as long as DPS wait to let tank establish aggro, and everyoine stops prio casts, the key is EASYYYYY