I have been doing the Black Hole Dailies on two toons for a week and a half now. Just got my schem drop yest for magenta +41 crit (yeah). The drop was inside the EOV heroic +4 area. The exact location was a mob in the room prior to fighting the security mini boss (before you go up the elevator the second time). This was, in my opinion, a RANDOM drop. I have done that mission 10+ times and never seen that drop. That mission is great for getting blue and orange drops, however, that was my first purp drop. In fact, I have only had one purple drop in the whole black hole area, and it was a random mob, and the drop was for a crafting mission.
In summation, the schematic is a random drop. When I have been playing the last sev days, I have been going out of my way to kill every mob I see. Having a sorc with force storm helps . Just keep grinding because it is going to be random and rare.
-P.S. Hopefully if you find it when you are with a group of people, they let you need when it drops.