Why dont multiple sch shield stack?

[Lyrica_Ashtine]

snip

Fine, I'll turn on the helpdesk mentality and assume your brain is in a glass jar on top of your desk.

For starters: This is mainly about endgame content. The more casual content (Crystal-/syrcus tower, dungeons etc.) aren't even worth mentioning or elaborating.

You mentioned two regens? I gave you numbers for one regen. One regen heals for 470-480 on average, 650-670 with Divine Seal. Which means that TWO regens will heal for 940-960 on average and 1300-1340 hp every three seconds. Still with me? Excellent. A scholar worth their salt has full control over their fairy and uses embrace manually. Scholars letting the fairy sit on /sic - or even worse: /obey and not do anything with it - might as well play White Mage instead of Scholar. Just like how Regen overheals every 3 seconds because the target's HP is full, so can a fairy overheal every 3 seconds with Embrace. But if you don't feel like having the fairy pre-cast it's embraces, your decision I guess.
Stoneskinning mid-battle has it's uses to prepare the tank (or anyone else for that matter) for big hits. Just like how a scholar worth their salt casts adloquium on the tank before the big hit comes in.

Just like how two scholars are a terrible combination, the same applies for two white mages. I'll give you some homework here and figure it out yourself why two white mages is a sub-optimal combination - just like how two scholars are sub-optimal. I'll give you a hint: Two white mages combo has a far worse MP efficiency than two scholars. But do make sense, rather than something that is "according to you".

[Cynfael]

just like how two scholars are sub-optimal. I'll give you a hint: Two white mages combo has a far worse MP efficiency than two scholars.

This is a good point. Two WHMs together are usually pumping out ridiculous overheal, and their DPS is not nearly as sustainable as that of the SCH.

Given the choice, I'd pretty much always take 1 SCH + 1 WHM for end-game content where 2 healers are desired.

For casual content, as I said before, it doesn't matter at all. Slop shields all over the place or blow your party up with HoT spam, because it makes no difference when the challenge level is low and the players are extremely overgeared. Two of the same healer isn't unworkable in most situations, just not optimal.