From Answers HQ:
"Hey, thanks for the report. We tested Hound's Tooth against the Imperial TIE Fighter (while Breached) and confirmed that the -25% Evasion is applied correctly.
It's probably a matter of perception.
Also take into account that the Imperial TIE Fighter has the highest evasion from all the ships. If it gets -25% Evasion it will still be able to evade like any other ship in game as it brings it's evasion to the same level as other ships."
It sounds like there is a base evasion stat that all ships get that can't be adjusted?