SCH's capstone abilities clash and contradict each other rather than complement each other.
Dissipate removes the core aspect of your job. (Imagine if something completely locked out the Fire spells from BLM) and stops fairy gauge accumulation. I've never liked Dissipate. If you're in a position where you need Aetherflow stacks NOW, you're in a bad spot and losing your fairy is not what you want to do.
Fey Union is clunky, and slow.
Seraph makes Dissipate pointless.