The reason for the reduced damage is that these are much easier to acquire. Verethragna is an awesome weapon, but it's approaching the difficulty of a Relic/Mythic to get 50 of the Two-Leaf Chloris Buds needed to make it.
These aren't a walk in the park to acquire either. You need 30 Coin of Advancement which drop from the 4 boss Morbid Mollasses on the Veridical Conflux 2, Walk of Echoes battlefield.