My main issue is that at higher levels of power, Psykers are not only powerful, but can annihilate armies without any risk of Psychic Phenomena. No Phenomena when fettering powers, which can still easily tear apart multiple battletanks etc with Holocaust or similar. Sure, being able to do this is cool... but I'd like to have some risk.
If the psyker can see the battletanks, it's at least likely that the tanks can see him. Which means they were rather sloppy, because that psyker should have been a stain on the ground for several rounds while he was still out of psy-range, but within battle-cannon range.
