Sev did say just today that the acrobat DCs would be getting a rework in an upcoming patch. Someone asked if that would also include the assassin poisons and, as far as I know, that has not yet been answered. So we can only hope...
EDIT: Even if a successful poison strike is not required to apply assassin's mark, it would be nice to not have to waste AP just to gain the benefit of weakening strikes and deadly strikes. So either take away the poisons as the method of applying assassin's mark, or make their DC the same as assassinate so we don't waste AP to get what's really useful about them – weakening and deadly strikes.