Tips for using her ult?

I have 34 hours on psylocke in comp now and I still feel i get little to no value with her ult and now I’m seeing all these videos saying how strong it is this season but for me if I go for a big group the targeting will just be awful and I’ll just end up tickling them all or if I go for a lone 1/2 supp maybe, they’ll just have some sort of mobility to get out easy.

Could I have some tips on the best times to use it pls.