odds of winning doesn't decide whether you win a battle or not
it's just a comparison of power between you and enemy. A full science ship (only SLB) can have 144k power but will be beaten by a combat ship with 50k power
The only problem if the hijacker have armor instead of shield, I already try to find a way to beat them easily, but can't find anything so far. It's very hard to beat them now
Hijacker's can have either armor or shields. I have faced one with shields. As for science ships. With all the manpower they tend to have, defeating them with a 50k power combat ship is not so easy. It is going to require multiple battles with that ship to do it. It would be like trying to blow up a science station. 50k is not enough to defeat it in one battle.