Combat progression for me pretty much ended at the Viper/Cobra stage. Even the Asp becomes too expensive to run if you're going pure combat. I nearly went broke when I did that, and have since rebought the Asp as a secondary trading ship after selling it to copy the A-rated Viper that nearly killed me in a war zone. Thank you for the inspiration, whoever you were, I've been having much more fun in it than I ever had trying to fly an expensive gunship for a military that doesn't cover expenses.
The problem with Viper is the abysmal jump range. I will take an Asp to warzones just because I don't have to do the tedious scooping every 2nd jump...