Power him up, man. Thats one of the best, or the best, defensive moveset in the game, and its an absolutely unique pokemon that not much people have. If youre lucky enough to have gyms near with low CP pokemon and can gain a decent position beside the low CP of Omastar, you have a beast.
I have power to his max a legacy Omastar with rock throw/ancient power (82% IV) and I'm really happy with him.