I would say put the 3 into imp. heroic strike. In my opinion, imp. taunt has always been a waste of talent points. I'd be paying 2 talent points that could be better spent elsewhere..for an 8 second taunt instead of a 10 second taunt.
Now, call me crazy, but I've never had that 2 seconds be what would make or break things. In the first place, if I'm losing agro that often, I'm PROBABLY not doing my job by either 1.) Maintaining agro properly, or 2.) Making the DPS focus fire. If agro is being ripped off of me that commonly, which I will admit I have had my off days, I need to get my sh*t together. The talent points aren't the problem, I am. But that aside, in those occasional instances where I just CAN'T seem to hold agro for the life of me, imp. taunt would never have been the game breaker. I'd normally have 6-7 seconds left on cooldown...and if it's only losing agro like that once or twice in an isntance, like it should be...don't rely on wasted talent points. Stance dance and hit mocking blow, or use challenging shout. You should know how to stance dance already anyways, think on your toes and utilize this important aspect of tanking.
Edited, Jan 9th 2008 3:32pm by FletusSanguine