Frostner's strength is not in its statistics. It has a higher knockback and slowing effect, it's meant to keep enemies out of range, not slug it out like a brawling weapon. It is very good at this, and also very good against most swamp monsters damage wise (only Abomination really resists is), sure, everything Mountains should be good against swamp, but most things take great increased damage from Frostner.

I personally struggle more with Swords, I know they're good, but they come so late I don't have them trained. In the Black Forest, Piercing damage is needed for Trolls, and everything else just dies to *anything*, and in the swamp, swords are resisted by almost everything, Bronze Sword is basically like taking a Club to the swamp, only more expensive, and an Iron Mace will do much better than an Iron Sword, so it's not until Mountain that you really can consider a sword seriously, and that that point, it's so far behind everything that it can be hard to justify the switch, when an Iron Mace and good Dagger can handle the mountains just fine.

This is where Frostner comes in, when you have a high Mace skill from fighting three biomes with Clubs/Maces, and low Sword skill, and need to take on Fulings, which really do not like Frostner. It's all about the decision of stopping and grinding sword skill, or using Frostner to smooth the way onto the Plains. I guess the deciding factor will likely be how weaponry looks going into Mistlands, maybe they're have a biome weak to Slashing, or we'll just end up with another Undead-feast and Frostner will punch above its weight again.