So my main is an Arcanist...

[Foo01]

Do you ever get to a point where your int is so much more than your mind stat, such that it makes sense to use the cleric stance for healing duty?

[Nahara]

The "mistake" is that they put that 10% boost and 20% penalty on the cleric stance applicable to the SCHs, that should only apply to WHMs. If it was just a straight up swap, then there is no issue. It would be sensible and straighforward to put all point in INT and when you want to switch roles, you switch stances.

It's not a mistake, because that's not the point of Cleric Stance.

Cleric Stance doesn't exist so that Arcanists can cheat the bonus attribute points, it exists so that healers can have some semblance of damage so they can do solo content (like quests and story missions), because nearly ALL of their endgame gear is focused on MND.

I wish Summoner could cross-class Cleric Stance, because then you can just dump everything in MND when leveling up.

See above. Plus, SMN's endgame gear (and a couple of their leveling gear pieces) are entirely INT based. They have no need for Cleric Stance.

[Wilan]

Do you ever get to a point where your int is so much more than your mind stat, such that it makes sense to use the cleric stance for healing duty?

Nope. Cleric stance reduces your healing potency by 20%, beside swapping INT and MND. It's meant to be a boost if you want to deal some additional damage as a healer, not to compensate builds.