If Yellojacket Skrull is facing a team of 4 Wild Cards and one Mystic if he uses his Trator SP and outwits one Wild Card TA. That means all the Wild Cards are outwitted and cannot copy Mystics for that round correct?

Yeah, but wouldn't a better solution be to outwit the mystic and make it so there's no mystic to copy, and then psyblast said mystic into unconciousness?

Sure, it would...

...but what if he's not within six squares of (or can't draw a LoF to) the Mystic...?

It doesn't counter "all wild cards". If he counters Legion of Super Heroes then it counters all Legion of Super Heroes. Spider-Man, Minions of Doom and Calculator would not be countered. You're countering a team ability, not the effect that the team ability has.