I have have been tanking a fair bit on my Warden (95, decent gear). Running a mix of Big Battles, 3 man, 6 man, and a raid or two.
In big battles, there are "specific" mobs that are designed to be tanked. These are most common in larger fights. These are normally elite master and nemesis level mobs. These are put in place for a real tank to pull and hold aggro. Their aggro table does not have any target priority set. All other mobs are not ment for players to tank. If you are finding you need to tank these mobs to succeed, you are missing the point of the fight.
As a warden, I normally run engineer. I find spamming conviction while OOC puts me on the top of the aggro tables for when a mob does not have a target priority.
Outside of big battles, tanking requires a mentality change. If you are trying to be a big an bad as possible, but your DPS is suffering, you will suffer holding aggro. For single target fights, I run 3k-5k DPS. You do not need to be invincible. Trust your healer more, and find a balance between DPS and survivability.
Beleag, Warden - Saelmundi, Rune-keeper - Nimerdale, Champion - Haldoun, Captain