This is my Modified version of the casting orders listed here. I don't do any of that math mumbo-jumbo and calculate .36ths of seconds and all that jive. I am not claiming to be the best, nor even close to the best Coercer on my server let alone worldwide. I do some decent DPS for any situation though. My casting order as it shows isn't just straight across but for the most part it is. If the skill below the top left bar are not up yet, I will use them. If MS is up I always use it right after Tahsiana, then continue on down the row on the top bar.
Sometimes if no spells that do any dmg on the top bar are ready, i will often hit Dissecting Gaze and Ego Melt. If I really don't have anything to hit i'll run in for a Shock Wave. I try to keep my spells and what they do in close proximity to other spells of that type.
You can see I differ than the recommended order by including a fast casting fast reuse spell inbetween the proc spells so that they go off. I always start out with Tyrannous Mind for the perpetuality increase on the pull to get more speed for casting the debuff first. The reason I do the debuff first is because often times the mobs will resist Chronosiphoning if you lead with it, but usually lands if you debuff first. I can go into further detail on why I use this order if you really want but I doubt mine is the best. I do less dps with the one at the beginning of this post...