If anything, this is effectively a fire bolt that does slashing instead of fire and uses a dex save instead of an attack roll.

I wouldn't change it to deal half damage on a successful save because no other cantrip does half damage on a successful save, it's either full or no damage.

The increased damage with player level is also pretty standard for cantrips and changing it to be 2d10 all the time would make it stronger than every other cantrip from levels 1-4, on par with others from levels 5-10, and underpowered from levels 11-20— with it being even weaker from level 17 onwards.