[quote=Tyki]
while we're on the subject of plot holes in the sc2 universe. if that was so then why did they need kerrigan to be highly psychicly gifted in order to convert her?
[/quote]

They didn't. Kerrigan was converted because the Overmind wanted to use the pschic powers Kerrigan possessed as a weapon. It could adapt to the guns and blades, but it wanted to use Kerrigan to develop a way to defeat it's ancient enemy, the Protoss.