depends on the omnipresent being, if he attacks in patterns instead of like, omnipresent attacks, and if their reactions are clearly limited and stuff, they would scale to their attacks and reactions
if they use omnipresent attacks and have infinite speed reaction or something, i think you might need ap and range or like, some weird ass dodging ability that lets you dodge, well, out of reality idk
if they are omnipresent across time and so are their attacks and reactions/mind, immensurable speed, cuz you are fighting stuff beyond linear time