Class trees (and guild trees) exist to allow a skill to be used by bypassing an item requirement. Ie DK Whip can be used no matter the weapon, Snipe can only be used with a bow.

Why not remove Whip from the tool kit and update the spammable of each weapon tree to have a morph akin the a DK. The Mag whip essentially becomes a morph or Destructive touch and the physical weapons get a molten rock themed skill (not poop shot) that also benefits from Seething flame or Stagger which seems to be the unique attribute of the DK tool kit spammables.

That way this weird attempt at trying to figure out what whip should be, what it should cost, which DPS should use it every patch can end.

There are many skills like this that could over rule 'standard skills' for instance the Sorcerer has a unique shield, the unique attributes of this shield should just over rule Light, Med and Heavy in their own unique way. The arcanist also has a shield that looks really cool, would be a shame if it ends up inferior to the generic Light armor skill and people use that instead.

Could probably end up close to losing a tree from every class, but having many more unique skills in each tree specific to each class.

I could see the DK just getting Molten Fists as the dual wield spammable where his hands turns to rocks and just belts the crap out of the enemy causing stagger. Same or similar base function, different animation, unique property (stagger).

Obviously need some consideration for passives extending to Class specific unique skills in weapon trees.