Where to start... oh, I suppose the best place to start would be "against AIs". Going up against a decent human player should be a real eye-opener.
One-on-one slug matches aren't really a very good indication of capital ship balance. Especially when you're dealing with support vessels. Sins is a fleet-based game, and its balance should be treated as such.
Sure, Akkans are arguably 'stronger' than a Dunov one-on-one... but neither of these ships are intended to fight by themselves. Try a pair of Dunovs cross-buffing each other sometime-- that's a pretty nasty juggernaut, especially when they start sheild-boosting each other.
Not to mention, your basis for overpoweredness is centered around keeping Ion bolt going when there's numerous abilities out there that will preclude that-- easily so. And I don't buy "if you don't use abilities" as a prerequisite. Just about any matchup where one capital uses abilities and the other doesn't is going to result in a clear win for the unfettered ship.
This is like saying you could beat up a boxer if someone tied his hands behind his back, and then saying it proves you're great at fighting.
I'm not even taking into account the effect of putting a Level 4 ship up against(given it's the AI) probably a level 1 or 2 ship.