I think it's difficult. The most base damage a Frozn character has is 5. This means that they are much too ability and bonus reliant to do enough damage to do well in higher ELO. It would take a lot of skill and luck to do well with them. They also need better characters at 2*. They are several pieces away from being competitive in ELO. Strompah is a great character but he doesn't address their needs.
A 5* with 7 base damage
A 5* or 3* with SOB
A topend 2* with at least 3 base damage, maybe an attack manipulator (6/3, Support: +3 atk)
They are pretty good at winning rounds though.