I was actually having a discussion today with someone about how I think Rumble's ult isn't very good. It just isn't visually clear what it actually does or why it does that.
When Anivia ults, you see a big swirling ice storm and you think "yeah, that's probably going to make me go slow and also hurt me as long as I'm in it.
When Rumble ults, you see a line of rockets land, and then leave behind some fire, and then disappear. I would expect that to do a bunch of up front damage, and then maybe a bit of burning damage over time, or maybe I would expect the rockets to explode at the end and do more damage if I'm on it when they explode.
But that's not how it works. Why does it only do damage over time? Why does it make me go slow at all? Visually, it just doesn't line up very well with what the effect is.