While this problem existed in DL and DA, it's really noticable when you can build heavy fighters with frigate level HP. The way leveling up works, you can end up with as much or more health after any given fight even after taking damage. In this sense, attacking a significantly more powerful ship with weak ones is a PHENOMENALLY bad idea, since all you'll do is increase its HP.

I feel that this unfairly stacks the game even more in favour of powerful, high HP ships. You cannot effectively use a swarm tactic against an opponent with higher tech, since the ship you hit effectively regains all its HP, to say nothing of anything else in its fleet.

As an alternative, I suggest that the leveling system be changed like this:
*Maximum HP rises as normal
*Normal HP doesn't rise at ALL outside normal self repair functionality

To justify it in terms of "experience", you could argue that the ships crew doesn't see the benefits of the new skills until they've spent time to reflect on what they did (ie, training during repairs).

What this would do is allow large, powerful ships to be slowly worn down by smaller ones, instead of such a tactic resulting in "feeding" the ship in question (which makes it effectively invincible)