Actually, you are wrong. I'm not saying this pattern is predictable, I'm saying his actions are. You can see him swing his arm, and there is some windup time before he could boost. Not to mention it takes some time to accelerate into his full speed, while being slower initially.

I never said Dante would aim to stay in a distance for the whole battle, but mainly when he does the ground sweep. With Air Hike and E&I, Dante can jump twice, and within each jump, he could sustain in air with E&I. Not to mention he could just-defense if he senses any danger.

Dante has fought more powerful tentacle-wielding creatues (DMC3), and yes, you better believe that he could dodge/parry/just-defense all the attacks and counterattack/just-release/DT explosion to end the fight.