Smite’s issue is its lack of downtime, particularly with Charged Smite. I’ve already suggested this 1,000,000 times… but make this 1,000,001.
Just give Charged Smite limited Uses that Regen on a Cooldown. Like Arbitrator’s Remote Detonation and Ogryn’s Big Friendly Rock. That way Psykers can’t just spam Charged Smite for the entire duration of the Mission. Y’know, actually needing to reserve their Charged Smite Uses for situations where they’d actually benefit the Team.