A thought on adjusting psychic spam:
1. Remove the army wide limitations on duplicate powers per turn, and per model
2. discount psykers keep to only 1d6 all the time
3. mid-tier psykers may use 1,2 or 3 dice as they see fit
4. high tier psykers (Maggie for example) get up to 5
5. Every time a psychic power is successfully manifested, the roll required to manifest that power becomes the successful roll for the remainder of the turn.
6. If a model tries to manifest the same power more than once, the result roll is increased by 1
The result of that is you can have screaming hell murder psychic powers... and then the warp comes for you.
Not a general purpose thing, but might be valid in matched play apocalypse scale