Right now there's a bug where SEF spirits are not benefitting from mastery, not increased. It's been reported for a few weeks, so hopefully it will get solved.
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That's possible, the sims have SEF doing what it's supposed to, so if the bug has them doing less in-game, that would explain why people are seeing Serenity being better.
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Those were their original class changes, many of those aren't around anymore. Much has changed since November.