Given his chosen course of action was neither to act like a decent person, nor to end the relationship cleanly if he thought he wasn't worthy of it, but instead to act out and repeatedly hurt his girlfriend to the point where it'd drive her to end things, Mina objectively does deserve better than him. Heck, probably anyone deserves better than him.I think there's also a certain amount of self-hate and/or self-sabotage going on, whether or not Ian is aware of it. His dialog reads to me like he feels, somewhere deep inside, that Mina deserves better than him, so he lies and cheats and pushes her away.
Mind you, i'd place large part of responsibility for this on Chuck's doorstep because he's the one who apparently taught Ian to prioritize his own needs and whims above all else, and probably had large share in shaping how Ian views women... but at the end of the day if i'm supposed to buy the idea of "oh but Ian is acshually such sensitive and good boy down inside" the game is half-heartedly trying to sell me, then i'm consequently going to saddle his firmly with ultimate responsibility for his own behavior, and what sort of a person he chooses to be.