White-mage is doomed - and why

[QooEr]

What is "invest heavily" in this context?

By invest heavily, i mean to even catch up on the other healers' mp restored per min. Let's put thin air as an effective +400 extra mp per min as a generous "case B".
For whm to match sage's mp economy of ~1833 extra mp per minute, it would need to restore 1167 more mp per min, or 767 for case B.
That translates to approx ~1287 piety for case A and ~843 for case B, for a lv 80 character in ShB.

Raw numbers are a bit confusing, so let me put this in terms of melds. 800 piety is about 13 grade viii melds. 1300 is 21 melds.
WHM would need to meld piety on half of its materia slots for it to barely match the base mp regen of sage, which has the second worst mp economy of the healers.

Most fights are around 8-12 minutes, so I wouldn't think it would need too much, especially with a co-healer to split the burden.

Fights do last 8-12 minutes, however you also need to consider the following:
- The time till oom was presented as full gcd uptime of only dps spells, which are our cheapest spells. Casting any healing spells whatsoever outside of thin air will only cost them more mp.
- ergo, The 7 mins is the optimal scenario because thats assuming whm never casted medica ii or anything of the sort.
- This is assuming 0 spell speed. having spell speed on gear only exacerbates the problem
- the very vast majority of players cast gcd heals that arent afflatus.
- if you die youre pretty much screwed

If you want a more comfortable gearset, if youre not very experienced, or if you just want to prog and want to have a cushion of mp, you would FIRST need to slot piety equivalent of 13 melds just to match what other jobs can do with zero piety melds. Any other healer with that much piety would be infinitely more comfortable regarding their mp.