The main argument for its removal, is that it is currently a mostly wasted button on the action bar.

It's predominantly only used during Trash in dungeons and for a few attacks on pull of a boss and that's it.

Outside that, it's DPS stance all day.

Thus its removal will be a net gain of one more skill (Due to SE wanting to keep to a specific limit of button usage)

Essentially, as it's already designed in a completely boring way and almost useless as is, there's no reason not to just go all the way and fully delete them from the game, in lieu of a more interesting and useful skill.

Personally, I'd rather they redesign stances, so that it's not DPS Gain vs Defence Gain (With a Damage Loss on top of the Damage Loss from not having the DPS Gain... Seriously SE, what's up with the double dipping on damage reductions?) because, unless they radically change how incoming damage works, no-one will care about the Defence Gain. This isn't even talking about the Damage Loss, which automatically puts it into disfavour because damage is literally the only thing to work on improving as a Tank in the current state of the game.

I'd much rather stances be more in line of conferring gameplay shifts. I.e. "Tank Stance" giving you skills that are reactive to incoming damage. Things like Shield Swipe and Sheltron/TBN. So, you gain DPS from actively mitigating damage. Thus making it ideal for when you're currently in the "MT" or "Active Tank" role. While "DPS Stance" gives more skills that are better when you're not taking damage. This can be things like positional attacks to play more like a mDPS, or it can be utility skills like Cover that allow you to protect other people from damage but requires you to position in a way that wouldn't work while actively tanking.

Thus making it so that there isn't a penalty for being in a particular stance (No passive damage increases or decreases) but more about changing how you play depending on where you need to be at the given point in an encounter - Which would help alleviate some of the inherent 123 ad infinitum spam that plagues Tanks (And is also never changing irregardless of what position you find yourself in...)