black hole only, the base is 0.2% so it scales from there - 100% useless tech no matter how u look at it, with base chance so low and gains so high from expos you wont even notice cargo going poof outside of week 1 new uni or 1x eco unis ( it still hurts)
t18 tech discoverer enchantment affects pirates/aliens chance ( base as disco is 50% and bonuses from t18 apply to that, so with 50% disco your chance to avoid is 75% ) and yes with 100% disco enchant ( 20t+ msu ) you will never encounter pirates/aliens anymore.
if pirates/aliens bother u so much everytime u send a rip on expo they run away too 
i would have to say by this description that is referring to t3 indeed , wording in Ogame was never straight forward, its either poor translation from DE or someone lacks clear and precise instruction writing skills
