Seriously it is far to strong. It plays out as an avoidance stat. That type of mechanic plays wonderfully with all the other mitigation stats. It is very unpredictable as to how much damge it will save a player from.
Before you think that that isn't true, consider that avoidance doesn't take into account the magnitude of the incoming attack. You avoid it you avoid it. Avoid a BO3 60k hit is equal to avoiding a turret's autofire as far as the stat is concerened. Resistances are a known factor we know exactly how much damage they will save us from.
The downside is the way defense plays into cruiser stats. Its way to low. There is no logical reason for this. None. Simply consider that defense decreases an attackers ability to hit a ship effectively and not "at all". Currently defense mechanic is an avoidance mechanic, it shows up as a miss after all. Some silly notion of 'speed tanking'. Oh okay, sure. The guys that can pilot a ship across the quadrant can't track another ship that's RIGHT THERE strictly becuase it's fast? Be serious.
There must be something else involved. Like electronic countermeasures, better shielding, stronger hulls, all sorts of "baked in" methods to assure that a ship isn't instantly locked on and vaporized.
But only for Escorts. The only way to gain defense is via tactical abilities. Please don't count evasion. Sure it's there. Yah you can doff it. Still Cruisers and Scis can't compete in the defense department with Escorts, yet Escorts can compete easily in resistances and heals.
Acc alone will never overcome Def. Def is way to high. There are methods to reduce a targets Def but the BEST ways to counter those methods reside squarely in the tactical domain and ALL the counters are available to Tac. And Def starts far to low for Cruisers and Sci considering they have no real ability to raise it.
At the least consider adding plus defense consoles for eng and sci. Construe them as electronic countermeasure or armor bracing consoles, but make them available. Have the ALSO reduce the chance to be critically hit. Is it reasonable that a dinky little ship can crit a cruiser out of existence in moments? Not so much.
Escorts need to have thier chance to be critically hit INCREASED. It seems pretty reasonable that you may miss an escort, but it seems equally reasonable that if you did, you'd hit something vital and not one of the five million holodecks, bars, lounges, crew quarters, cargo holds that a cruiser might feature.