There have been a couple of times where I was watching my cooldowns a bit too closely and I noticed that Barrage was ready and Empyreal Arrow was almost ready, so I occasionally decided to pop Barrage in advance.... but really there was maybe a second or two left before Empyreal was ready, so of course I should use a skill or two in the meantime! Oh.... no, wait my........ oh well.
Also, I'm kind of new to Ninja but I still mess up Sneak and Trick attack sometimes as well. *sigh* !