I didn't mention that there are points which can be easily moved around in the skill tree, but you're not wrong. Just because Diversion can't be used on bosses it doesn't make it useless. There are a few situations (droids in TC, Regulators in NiM OP IX) where an accuracy reduction on an add can be pretty useful, acting as an extra cooldown for the tank.
Kneecappin' and Heads Up are totally interchangeable though. I use leg shot every now and then, but if you find the speed boost to be useful then take it.
Awesome, thanks for the insight, the Op IX adds hadn't even crossed my mind. Good to learn something new everyday.