Krillin in dbz was just there as a keepsake from the old Dragonball. Much like Tien, chaotzu, and Yamcha, these characters were all about continuing the story, but really did jack for it.
I'd say krillins biggest part in dbz was dying at the freeza saga. Because thats when goku snaps and finally becomes a super saiyan. Sadly though most of the original dragonball characters have nothing better to do than die or fight someone not important.
Piccollo did 10x more important stuff than krillin.