Both killer AND survivor will get a tremendous skill check upon the survivor being picked up.

If the survivor HITS it and the killer MISSES it then the survivor successfully executes the decisive strike.

If the Survivor MISSES and the Killer HITS it then you lose your decisive strike as the killer outskilled you.

If Both Killer and Survivor HIT or MISS the skill check then the decisive strike will not be used BUT the survivor may use it later (if picked up in anyway)

This would give decisive strike a counter and base the perk on a battle of skill rather than a free escape if you were "tunneled".