I think their rotation is fine. What I would like to see is instead of Ice Lance and Glacial Spike cleaving, I think instead when a spell is Shattered it causes shards of ice to erupt from your target and hit enemies around them. This is a fantasy that Path of Exile leans into with a number of their frost abilities and it’s very gratifying to make frozen enemies explode in that game.
I’d rather see the cleaving ability improved for Frostbolt (i.e. making a dedicated Frostbolt ‘cleave’ build).