Sorry, but i'm newbie and dont know if this will be later when I grow up !
The matter is that when I focus near on a orun collector ship, then fire, that bot break and shoot me until I destroy it.
I wish, almost, sometimes they run away and I'll need to hunt it.

They used to do that, but it gets really old, fast. The problem is that at lower levels the bots can run almost as fast as you can - and they tend to do it in a straight line. So you never catch up. The collective outpouring of annoyance back before the public release over this behavior caused the devs to make them stand and fight more often.

there still are some bots that run away, almost all will defend themselves though.