Dont most good hiemers use ult rockets for kills anyway?
They usually use Ult E in teamfights or Ult Q to 1v2 since it offers overall more damage, Ult W is extremely situational because it needs to be used on targets who cannot dodged it while there is no one who can bodyblock it.
Won't make him any less cancer and doesn't effect his better ult group stun in any case.