Personally, it feels terrible to play champions with no mobility, simply because it drastically reduces out-play potential.
For example, as Taliyah or any immobile mage, I feel like I can't do anything against a Zed or Akali if they ult me without me blowing flash or using hourglass.
I don't feel like they outplayed me when I'm full health under my tower and they still dive and kill me just because I didn't finish my Hourglass or my flash is down.
If I'm playing Ahri, or Lucian, or Kassadin, or anyone with mobility, A Zed ult isn't an insta-death sentence.
I'm very glad riot is giving every champion now some sort of mobility, it feels terrible playing anyone immobile against certain champions (being ulted by Zed knowing you are gonna take the full force of all his abilities, being run down a lane by Ashe slows, getting grabbed by Darius, seeing some important ability flying twords you like Morgana Q and being unable to avoid it in time because your character doesn't have mobility and you were being over agressive).
And no, items like you suggested are not the solution. Zed ult is completely countered by Zhonas, but that doesn't change the fact that it feels terrible to be dove under tower and not have flash or Zhonas up, with no counter play.