I had a Red Mage in Malikah's Well literally spam Vercure four times after they took 5,000~ damage.

Just let that sink in that they spent 2,000 MP on what is easily healed by Medica II, Indom/Whispering Dawn or Helios/Asp. Helios.

I don't think MP is the issue, I think the player is the issue in this situation.