As it stands, the Blackrazor greatsword is a disappointment........ I did not test the others, but Blackrazor is downright saddening.
I suggest that a raid be added to the quest arc where said weapons can be upgraded to become closer to the iconic weapons they are attempting to imitate.
Echo Of Wave could gain an ability to summon a small typhoon with man-eating fish
Echo Of Blackrazor would gain the Legacy version of Vampirism along side a version of Cursespewing effective in legendary quests, alternatively Echo Of Blackrazor would also be able to be upgraded into being a Bastard Sword.
Whelm.... I don't know enough about this one to be honest..........
I ran the White Plume Mountain quest, and honestly...... those three weapons just aren't a big enough part of it, it feels wrong..... like this White Plume Mountain quest is an april fool's day prank and the Real White Plume Mountain quest is a raid yet to be released on Lamannia let alone even so much as mentioned anywhere else.
I ran the white plume mountain quest three times and each time rerolled all of the chests the max number of times, never did I once see one of those weapons from any of the chests neither from my chests nor the chests of a party member.