Karthus' ultimate needs to do more than just damage

Right now, Karthus' ultimate might be fairly potent, but it's too easily countered, rendering its only effect moot point. and the like all hard-counter Requiem, and various Champions (especially a lot of newer ones) can completely negate the damage with their abilities. As such, Requiem has become far too binary, and as a result, Karthus hasn't been a popular pick for ages (even if his winrate is decent).

I then look at a similar ability in Heroes of the Storm, Mephisto's Consume Souls. This is basically Karthus' ultimate with a lot more utility; it not only does damage, but also reveals all enemies and slows them alongside its damage. The damage also isn't overloaded, making it much harder for him to use it as a finishing move.

While I'm certain that adding both a reveal and a built-in slow onto Karthus' Requiem would be impossible (read: far too strong), the reveal effect at least could prove a good improvement to Requiem. Exposing your enemies during the channel would allow your teammates to see the enemy and dive in on them if Karthus can't finish the job, or allow Karthus to reveal their positioning so an ally can perform a dive.

And before you say "Twisted Fate!", there's nothing that says a global reveal should be exclusive to one Champion only. Besides, TF uses his ultimate also as a long-range teleport and the rest of his kit lets him pull off some deadly ganks, so comparing him with Karthus is unfair.

Karthus really could use this improvement to his ultimate, as it's presently too singular in function.