The problem with the TIE striker and U-wing is that they aren't star fighters. As far as we know the TIE striker is an atmospheric fighter, and the U-wing is a troop transport of sorts, like the landing craft from TFA.

Where did you get the info that the Striker is an atmospheric craft?

The only info we have on it says they are deployed from star destroyers and designed to dogfight x-wings and other starfighters.

So it's only an atmospheric fighter in the sense that it can operate within an atmosphere - just like most other TIES and Rebel craft