My main gripe being it feels like the odd one out.

WHM is superb at healing

AST is good at healing and/or shields

SCH isn't superb at healing, isn't the best shield deployer in most cases, their shields feel weaker or on par to AST, they aren't very damage dealing, they don't have a lot of support abilities.

It feels like in endgame content, they are rendered mostly pointless as AST and WHM can give shields/reduce raid wide damage respectively with much less effort and resources while bringing a lot to the table.