If we nerfed SCH's DPS rotation to practically mirror WHM/AST

[Sebazy]

And while they didn't have infinite mana in raid settings (they still needed mage's ballad if healing and let no one tell you differently), they could literally DPS for days with constant low-mana cost casting which is something neither WHM nor AST were able to keep up for anywhere near as long without going out of mana.

^ This

During early A12S kills, my SCH partner literally couldn't raise or he would go OOM during the fight. AST had it far better during 3.4, I deliberately ran myself to near OOM at the start of the last two adds but aligned Shroud, Synastry, Lightspeed and CO to ensure I could both solo heal them and regenerate most of my MP back in the process.

Scholar was broken for a lot of reasons

You need to understand that SCH in itself wasn't OP. Rather AST/SCH was the best overall healer comp by a rather significant margin (assuming all players were at a reasonably even and high skill level). WHM/AST was generally a significant downgrade in healer DPS whilst WHM/SCH gave up that oh so delicious balance card, not to mention both alternatives had to deal with WHM's comparative MP starvation at the time.