It worked in 2.0 because there was only WHM/SCH. There was no alternative. WHM didn't have the oGCD heals, and SCH was limited to Shield Succor. Today Indom is OP, and AST also has mitigation that WHM never had, and stacks with SCH.

I remember helping a Duty Finder Turn 13 clear in the day as SCH/SCH and our Succor-spam was the scariest part of the fight for the Stack/divebomb/run since no Cure III. (Please crit, so people that don't get topped off live). Not to mention weak-protect, which I think the 10% echo took care of in a sense.