There are a few things I think could make the psyker experience better
first off, head pops and the lightning staff sometimes has a hard time targeting enemies through fences or behind cover, even though your teammates or the AI can shoot through the fences, it can sometimes make using your psychic abilities very frustrating and feel clunky. The headpop targeting does not always prioritize elites either, as there are many times where I have a highlighted elite surrounded by chaff or traitor guard that takes several attempts to correctly target.
The other issue is the effectiveness of many of the staves, as well as some of the talents. The soulburn talents just are not particularly good, they do not proc often enough and effect too few models for how little damage it does at the lower stacks. Wrack and Ruin should have a much larger range of effect, doing 7 damage a second in a bigger radius is not overly broken IMO. And talents like psykenetics wrath (which boosts force weapon damage) is extremely minimal. I’ve done some bro science experiments in the meatgrinder with 6 stacks of warp charges and max perils, and it does raise the damage but not enough in my opinion to be worth it over the other talents. The trauma and purgatus staves are really lacking as well, the purgatus staff should excel in clearing hordes but I find it’s killing power against the fodder enemies to be pretty insuficient given how much perils and charge time it takes to kill anything. A bit of damage increase and maybe lowered perils would help make them feel useful.
And finally, it would be nice I think if there was better intergration between force weapons and the psyker’s talents/abilities. The Force swords alternate could easily be considered a head-pop and give warp charges on kills IMO, and the talents should benefit force weapons more than a slight 5-15% damage increase, triggering things like wrack and ruin for soulburn builds on force sword alternates or maybe a 15-25% chance on some force staff attacks for example.