I've been storing the Trisword and Whurrgarbl in the locker since I found them but now there's no real point anymore. I might still buy them in a dungeon as the last item before taking on the boss if I have a free slot but as a preparation they're just hogging important space.
The bosses are usually hard enough that if I need to spend more than one or two potions beforehand, I may as well retire and try again.
Viper Ward & Soul Orb changes: Yes!
Venom Blade: sounds like it would now actually be very useful. Blast the enemy with BURNDAYRAZ, then attack once with melee. Enemy is poisoned, then regen to 100% by exploring and return to kill. Then repeat with the next enemy.
It's pretty common that against heavy hitters you couldn't handle two melee hits in a row in any case.
EDIT: The update changes listing implies it will only lose it's poison for the enemy you're currently fighting and will work again for the next enemy, Darvin's comment implies it would lose it's poison for the whole dungeon run. Haven't yet verified which is correct.
EDIT2: Yep, poison effect works again fine for the next enemy.