Why are you acting like the WHM is so inferior in everything? More than anything, what you are describing is a hypothetical situation with top-tier players where they have mastered the content and try to push the runs to just a tiny bit faster with the off-DPS potential of 2 stacked scholars. Even then, due to the subpar synergy (compared to SCH/WHM), the scholars will have their hands more full than they would with a WHM partner, relatively speaking. Sure there are some instances where the raid-healing is very lenient for the most part, such as Turn 9 which is solohealable anyway, but that doesn't mean the WHM is suddenly useless.

A WHM can put out single target heals worth of 585~ potency without much mana loss over time, without Divine Seal, simply by Cure 1'ing, having Regen up and Cure 2'ing upon Freecure proccage. When Divine Seal is up, this becomes about 760~. That's not bad at all for a healer who is supposed to have its niche in raid-healing, burst healing and on-demand healing. (And that's just for the "maintenance healing", don't even get me started on the full-burst potential).

Yes, scholars are powerful. Yes, I don't mind playing with a skilled scholar. No, WHMs are not bad.