That's more or less what I'm saying.
Normally, on a Hawchafish, my strategy is to single out a ship, knock out most of their weapons with Heavy Clip, move in close, Burst Round everything else, Gatling their armor, and either Charged Rounds or Greased Rounds their perma-hull.
Simple, but effective.
When I say 'being in a bad spot' I mean that:
1) My Manti was sniped out while I was closing the distance for burst rounds.
2) The other ship kills my ally unexpectedly and turns on me mid-engagement.
3) A surprise attack while searching for the enemy.
All of these situations cause my engineers to switch quickly from offensive to defensive, and while the engie on my starboard Gatling can get to the hull quickly, the other has to run from fixing the engines to the hull, and in some cases, someone has to help tend the main gun. These precious seconds lost chip away at the un-fixable perma-hull.
If everything goes according to plan, than yes, the Bread and Butter of the GoI armada is quite durable.
It's the lack of ability to get most of its durability back after a close fight that keeps this ship from being OP.