First, make sure it is an Elite, and not say just a Tyrant King. If it is, then no, as long as you are in a party you're good. It doesn't matter who in the party kills it. This puzzles me as I have never had any trouble getting the schematic from the Tyrant Elite.
My bad, i spent a day killing the tyrant king with it's 30 minute spawn rate lol, didn't notice the elite right behind it. Thanks much! Finally got my CG skill (y)