Combat can definitely be a little unforgiving. Personally I've found that the best thing you can possibly do is simply to pick the right ship for the given situation, as going up against a Slylandro probe with, for instance, a Zoq-Fot-Pik is a waste of time and resources, no matter how good you are. Sadly, the only way of knowing which ships are effective against which is by experimentation (which therefore involves, most likely, lots of failing / dying).

In addition, never be too proud to run away from a fight. Some fights are either best avoided altogether, or avoided at least until you find the right alien race with which to combat them effectively. You'd surprised to find just how few fights you actually have to get into during the course of the campaign. Although obviously you want to have a few scraps here and there, since that's part of the fun.

That said, I've noticed as you have that the earthling cruiser is surprisingly versatile ship. So don't be afraid to use it.

Then again, I'm also of the opinion that some ships are hopeless regardless of the situation. Period. FIghting with them is usually just an exercise in frustration. The Shofixi is one such case, as are the Syreen, the Illwrath, and the Arilou (to name some). Just my personal opinion though. Arilou *can* do good damage if you're fortunate, but for me those situations are too few and far between to make it worhtwhile, and they are never certain since you never know where you're teleporting to in the first place, and second, the high speed and insanely sensitive turning rate mean that you sometimes actually steer into projectiles while trying to avoid them.