None of that makes sense.

I main a WHM so I'm not speaking from a bias:
-We (WHM) have to change stance to deal any reasonable damage, which prevents us from being able to pinch heal if we use it out of turn.
-Our damaging spells can miss.
-If we heal for 2000 on a party member who needs 1000, 1000HP of healing just disappears, never to be seen again.

-SCH can deal damage and heal at the same time.
-SCH spells don't even require the calculation of accuracy.
-If a SCH heals for 2000 on a player who needs 1000, that player gains an additional 2000HP in the form of a shield. (this is an exaggeration of the shields power)
-All that aside from having 3 insta-heals every minute, the power to soak up MP in an instant, granting haste to the entire party, having their own HOT, and damage mitigation with supervirus and e4e.

Regardless of weather it's programming, or mechanics, etc. the end result is that SCH lacks many of the disadvantages that WHM has to deal with.