Sure it is. It's good on plenty of champions that don't hit combo's a lot. While there are usually better runes for most champions, you can still play it. It's quite good on ARAM, URF, nexus blitz etc as well. I like it on Kayn personally, though Karthus is another one.
It's pretty good on an aggressive AD cho vs squishy ranged top. It's also pretty decent on Zoe, though comet is usually better.
Yeah, it got overnerfed so now it's only viable if you want something that procs on long range abilities...and if Arcane Comet isn't better.
Since it's a universal rune that works on every champion, either it's broken and you see silly stuff like dark harvest Soraka, or it's useless except on one champion ( Karthus). Frankly it's a game design fail and I hope they revert the change.
It's good on Karthus still. I think on any combo/burst champions, Electrocute tends to be better. DH can be okay if you aren't hitting a full combo, though it has to compete with Arcane Comet. Lethality Varus might be another candidate.
It's pretty good on an aggressive AD cho vs squishy ranged top. It's also pretty decent on Zoe, though comet is usually better.
Since it's a universal rune that works on every champion, either it's broken and you see silly stuff like dark harvest