I am terrible at this game and for now I've been playing against the AI before getting back into ladder. The protoss AI usually builds a deathball and protoss units are all clumped up together (esp. when collosi are in play because they don't collide with ground units) to the point where it's impossible to see high templars. Do you usually scan and EMP every unit with an energy bar?
Ya, just scan before you engage and emp everything, temps will either be in the middle of the ball, or behind it(although some protoss will run 1 forward to try to get off a storm when your not expecting it.)
Wait, high templars or dark templars?
High templars. I played against the AI that clumped all its units together in a ball. High templars were not visible at all because they were under collosi and in between stalkers. Quite ridiculous. All I could see were the energy bars. (But then again, they could be sentries.) I'm a little upset that Blizzard made such unit hidden so well, considering it's harder to EMP specific high templars than to storm at any group of MMMs you see.