The real problem with SCH, AST and SGE is that their limit breaks require the team for them to be used well. If you go them you are essentially griefing your team. WHM is the only one that is reasonable but with how other jobs are, it is "not good" instead of griefing like the other healers. AST's is the funniest, 30% dmg for the team that reduces over time! Awesome figure out how to time that effectively with your non-premade, quick chat!

They should get stacks of healing for damage they do. That is how you balance spam healing.