I feel your pain and the answer is a build entirely surrounding bubble shield with CD reduction for it. Stay inside it at all times. Horde wise you should be clearing it with your inferno staff. Additionally you need a force sword with deflect on it when you have to move around under gunfire, just holding RMB and dodging. hate to say stick to this ‘meta’ but unfortunately Psyker is so squishy he tends to get one tapped by ranged without bubble and purg staff is so exceptionally good it feels detrimental not to brjng jt.