A few suggestions for hirelings...

[My2Cents]

Off the top of my head...

Allow users to determine whether healer hirelings are heal-only?
Allow users to determine threshold where healer hirelings heal <---
Allow users to tell healer hirelings raise/heal me immediately, run from battle if needed.

Allow more than 1 in-game hireling somehow, more plat maybe? Alternatively, allow hireling contracts to last longer for us slower players, or make some form of contract all day or permanent.

[Merlin-ator]

Yes
They're already good at not wasting mana on unnecessary healing spells.
Goes for pretty much every player
You already can. You can have up to 5 gold seal hirelings out at a time. The MotU Panther Figurine acts like a Gold Seal without a timer on it. You could also have 1 normal hire and 4 gold seals.