Disrupt Destiny has probably been the least popular Psyker keystone since its introduction, owing largely to the fact that it puts Psyker in conflict with their teammates, who will often unknowingly “steal” the Psyker’s kills, while it encourages the Psyker to go out of their way to target enemies who are often not priority targets.
Allowing teammates to see the targets highlighted by disrupt destiny, and awarding the Psyker with stacks, regardless of whoever scored the kill (Provided they’re in coherency) would go a long way towards fixing the issues with Disrupt Destiny. The benefits of this would be twofold. Not only would the Psyker in question be supporting their team by highlighting targets who might otherwise be difficult to spot, teammates would also be able to support the Psyker by eliminating those targets. Transforming a feat that introduces conflict and suboptimal play into one that promotes team-play.
TLDR: Allow teammates to see enemies highlighted by disrupt destiny, and award Psykers with stacks no matter who got the kill.