Have you heard of Shield Mitigation?
This thing reduces incoming damage by a high percentage when a ship receives high damage. Basically any ship receives 0.1% of shield mitigation per damage taken and loses 1,25% per second, which means that a constant damage of 12,5 DPS will keep your shield mitigation maxed.
Now, frigates have their shield mitigation capped at 60%, cap ships have it capped at 65% and that increases by roughly 1/9 per level, giving you 75% max shield mitigation at 10th level. Advent also has means of furtgher increasing these numbers.
All in all, when a ship has 70% shield mitigation, 70% of the damage you deal to it is mitigated, nullified, ZEROED.
And there go the Phase Missiles - they bypass shields AND SHIELD MITIGATION.
Every 10% of a chance to ignore shields when an enemy ship has 65% shield mitigation means every tenth of your missiles deals 100% damage instead of 100%-65%=35% damage. This means that your missiles do:
90% of your missiles do 35% damage + 10% of them do 100% damage = (Maths incoming!) 0.9*0.35 + 0.1 = 0.415 .
So, A normal weapon does 35% damage, while Phase missiles with 10% shield bypass chance do 41,5% damage. 41,5%/35% = 1.1857.
Translating this to a language of casual Sins players, a 10% increase of shield bypass chance means that you will do over 18% more damage.
Add to this the fact that you are actually hurting the enemy ship's hull, not shields (and taking out shields doesn't kill the ship while taking out its hull DOES), plus the fact that all Vasari strike craft use phase missiles...
All in all, I've killed dozens of Advent level6+ capital ships that had well over 1500shields left when they went puff under my Assailant/Bomber fire.