Actually, at the moment, taunt is a bit messed up. I've /bugged and /feedbacked about it as well.
Playing my Warrior (lvl 54, Taunt skill roughly 210+) I've noticed that even on a sucessful taunt, I do not gain aggro about 50% of the time, if that. This has been around since a patch a few weeks to a month ago. It goes without saying that this is getting to be a bit annoying. Using CHoS main-handed with the 50pt fire proc from Nro, and SotBS in secondary with 75pt poison proc from EC,(have also swapped these and didn't see much of a difference) with dex buffed generally between 225 and 255, haste (spell + 31% Item (soulscream belt)), using provoke (all that's available till 55?) and maxed out skills. I still fail to regain aggro on a successful taunt. Also, there seems to be about a 50-75% fail rate on taunt to begin with, so this makes it even worse.
If this wasn't so common, I'd chalk it up to bad timing on the taunt (say, I use it when mob pings to the cleric, I hit taunt a split second before the wizard lands a 5k crit nuke and it pongs to the wizard), but that hasn't been the case. Lately it's been *very* hard to hold aggro at all without an overly long hate building period before everyone else engages.
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Pallies have been the favored tank while on my enc, for the pure purposes of holding aggro from the beginning. Landing Tash + Slow on these mobs on inc is possible with a good pally landing a stun or 2, but not with a warrior. Of course, a warrior will generally (not all the time) have better mitigation, hps, and AC (close though), so they are likely to live longer and require less healing. Also of note, neither Pallies nor SKs receive the Bellow line of abilities. They are given to Warriors only. (Knights get enough spell-type things to get aggro, they don't need more :p).
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Asking for taunt to be no-fail beyond 200 is a bit much. There should always be a chance for any skill to fail, no matter the skill level. Even a master of a trade can flub up occasionally. Again, this was pretty much ok until a patch a month or so ago. (Pre Dx9 patch...I'm thinking around the GoD release.)
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One last thing, there comes a point that you are doing everything you can to keep your max hate up (Provoke, low delay weapons with stun procs, proximity, kicking, making faces, etc) and you still lose aggro. At this point, the group members getting aggro need to lower their amount of generated hate. Using special skills, abilities, spells, cycling attack, and increasing the distance are all ways to lower your hate. There may be more, but I'm rarely ever trying to reduce my hate ;).
Edited, Tue Apr 13 02:01:12 2004 by cafeenoftheazurestorm