three reasons why not:
1- Weapon skills must be used. Giving stamDKs or stamsorcs a class spammable means your will not be using those skills. Then at least 3 lines will become pointless.
2- Stam whip will not bring anything new to the game. Just a mirror of magDK with basically the same problems. Both of them will be played EXACTLY the same.
3- Lash is crap. A stam whip will be even crappier than lash. The entire ardent flame line is crap. It is the offensive line of DK but it gives no bonus to dmg done. And even worst, those skills have a unnecessary snare associated, so, if you want a stam whip, first you need to aim for a rework on the ardent flame skill line, especially its passives.
Finally, *** the idea of class identity, if you want to trade viability for identity then you are clueless. Currently StamDK is viable, it is the best class using weapon skills. I prefer 1000 times to reinforce that concept rather than going to the poison meta ZoS has given stamDKs, which brings nothing to the table. A stam whip means we are going in the same (wrong) direction: knights using poisons. And that is far, far from the DK class identity of a knight using fire and weapons.
I don’t see why noxious breath is still so underwhelming. Short range and low damage, especially compared to sub assault. Maybe buff and rework this skill before having a Stam whip morph..?