I haven't had much trouble. If a rocket misses you have 2 more, you can also jump straight up and shoot down at his feet so if it misses just to the side he still gets nailed by considerable splash damage because of the massive blast radius, this has the benefit of reducing the chance of a team mate walking in front of you and you blowing yourself up. The only launcher I have with tracking is truth but I haven't used it on Crota and don't have much trouble, he is big and moves slow until he rotates. It takes practice but I got plenty of that with the ponderously slow Halo 1 rocket launcher.