Does upgrading ships with phase shield make ancients unable to hit you? Since they need to roll 6 + 2 - 1 = 7 which is impossible? so getting a phase shield u can send an interceptor with it to an ancient and kill it automatically?
Nope, rule book did mentioned(somewhere in combat phase section):
"Rolling a 6 is always a hit and rolling an 1 is always a miss, regardless of any bonuses the Ships may have."