If someone has the Domination tree, they potentially have Ultimate Hunter. If they have Precision, they potentially have Presence of Mind. The only way I can tell if they have those runes is to witness them either proc enough runes to narrow it down or witness them cast two ults closer together than would be possible otherwise. That means until that happens you cannot time the ults of people using these trees precisely. If the game would just tell me which goddamn runes they have, the only added thing I need to track for both of those runes to estimate an enemy ult timer is the killfeed that is obvious and broadcasted to every player.
Other situations where the lack of clarity fucks you:
* You think you might have a chance to trade kills with your killer in a close fight via some post-death damage source, too bad they had Triumph or Time Warp Tonic
* Got just barely enough damage to burst down that squishy? Well they had Time Warp Tonic, Nullifying Orb, or Bone Plating.
* Wanna space out your CC chain to maximize overall CC duration? Turns out they had Unflinching and since they just recently used both summs the tenacity you didn't expect bought them a window to mash out something to escape your chain.