Why the difference in duration?

[DevilsDontFly]

I mean, WHM also has Assize for MP while AST needs to rely on rng for the mana card, and most of that time the mana card is going to be burned to provide aoe bole or arrow to the party. The only reason for a WHM to be completely out of MP and/or having MP issues is if they have to constantly keep raising party members (which is not your fault as a WHM to begin with, and also applies to AST) or if they are heavily dpsing, which they can do far better than an AST anyways. Feels balanced to me.

[Eul]

But AST that can put their MP back to 100% after dying (for example) by LA + Ewer + CO, while WHM can't fully regenerate MP with SoS + Assize.