worries about combat

Yeah and also stated in the other thread it is not purely based on HP even though HP will be a factor in the combat system. Im not sure of the maths myself, but im sure if it can be exploited Brad will fix it in future updates.

If I recall right, it goes for whatever ship has the highest damage to lowest defense ratio.

Yup, Foogsert, that's what I remember as well.

I understood it to mean that the first target is decided by weighing up target power against defence/HP, with more powerful, and more easily destroyed targets attacked first.

Eg.
two targets with the same DEF and HP, but one has a higher ATK - target the more powerful ship first to get the biggest threat removed.
two targets with the same ATK and HP, but one has a higher DEF - target the lowest DEF ship first, so you'll be facing just one ship earlier.
two targets with the same ATK and DEF, but one has a higher HP - target the lowest HP ship first.
...With everything inbetween being a calculated tradeoff.

That's certainly how I'd generally be doing things if I had to prioritise manually, and from what I read, is how it seems to work (of course I can't wait to try it out for real tonight )

I don't know if marioflag was talking about my post in another thread, but I actually asked that question and said that it was my impression the enemy fleet went for the ship with highest hitpoints. But I'm at work now and cannot check. It is also possible that it was due to the beta and it may have been changed since (which I asked too).

Now that being said,

The example I mentionned was, let's have a fleet o 3 ships one smal and 2 mediums. The small one has a lot of experience, and its hitpoints reach 45-48. The 2 medium ships are brand new an therefore with its base hitpoints only (I don't remember, but something like 22-don't remember exactly).
The medium ships had more defenses and attack than the small one, but less hitpoints.

I had the distinct impression that the only ship fired at by the enely defending fleet was the small one.
On the other hand, I might be wrong, and another element interfered: I have a military starbase that adds defense and attack to the ships, so maybe with the bonuses, the small ship ratios seemed more threatening.

I don't remember exactly how the battle went because I thought about it later, womdering if I could build a fleet of a medium ship with lots of defenses to attract enemy fire and fighters with only weapons and no defenses to attack.
I wanted confirmation of this from someone more familiar with galciv2 than I am