I definitely concur with the above thoughts on taunt. Even before BC and mangle was introduced, I always tried my best to save my taunt for emergencies, when breaking crowd control, or if I was slow to generate threat (back then, even KTM wasn't around, so it was largely done by intuition). Post-BC, not much has changed in that regard and I do much of what was mentioned above. An opening mangle miss I can live with, but missing mangle then a dodged lacerate almost always ends with me mashing taunt next, along with (hopefully) a TS warning saying that I need a moment longer. I also tend to use taunt to get quick aggro on a second or third mob when tanking multiples, especially if I'm expecting a big heal early on (heroics, mostly, but also Karazhan). After that, I just tab-lacerate (similar to sunder in threat generation) a few times and periodically re-lacerate each...I rarely lose their attention after that.
Something I've noticed post-BC in damage classes is the complete and utter lack of threat control...or even self control. Pre-BC, it was commonly understood by higher-dps classes that waiting for 2-3 sunders before opening up was a good idea. Hunters could get away with starting early due to feign, but even that was spotty at times (yay resists). Now, though...ugh. People see a taunt go up and assume "taunt means GOGOGO" *facepalms*, and same for mangle. If you're reading this as a damage class, PLEASE FOR THE LOVE OF THRALL wait to unleash your personal brands of hell until your tank is sure to have the mob's attention. This goes double when the tank is trying to keep the attention of multiple mobs. In those cases, they need to build up threat on each...starting early and having him/her blow their taunt to save your ass often leads to the second/third mob smooshing the healer in a hurry. If you crit a ton (Verissi does and always has, so I know this well), waiting extra-long to start then going nuts doesn't help your threat as much as just doling out the damage slower, e.g. wait a second or two between casts...and if you crit 2-3 times in a row, stop casting if you think you're about to get an angry mob heading your way. I know it goes against everyone's nature not to keep spamming buttons, but sometimes it's just better to sit there for a few seconds doing nothing if it prevents chaos.
One big tip for tanks and damage classes, do NOT rely on Omen/KTM. More about the threat system has been disclosed, but it's still largely a "closed box" system that we don't have hard facts about (just relative numbers and observation). As such, while your threat meter may say you're fine, you could still be over the line (or still need to work a bit, in a tank's case).