Not enough toe in can cause dartiness as could too much negative camber, which it looks like you may have had previously. What you should keep in mind is the normal specs for STS's call for .5 - 1.0 deg of negative camber. The fact that you wore the insides of your tires out does not necessarily mean the alignment was waaaay out but, perhaps only a little. You may not drive your car into turns hard enough to use the rest of your tires
(yes, that means you baby it). You car may have to be aligned out of spec to help your situation. Ask them to use 0-.3 deg of positive camber and see if that helps also to set you toe in to the max setting(I don't know what it is).