If it's anything like the gorget, the additional damage from the weaponskill would have to overshadow the next weapon's DoT to make Seismic Axe worthwhile. Somehow, I doubt it's anywhere near Perdu, or even Byakko's.
Yeah I didn't think it would when I got this I was originally after Zha'Go's Barbut which I didn't win. The only thing I'll replace my Byakko's Axe with is Perdu Voulge. the Seismic Axe is just a new toy for me which ill eventually get bored with and be placed in the back of my MH to collect dust