This is a huge nerf. You can no longer barely clip someone who's escaping around a corner with an angled wall, to then E them because you can't see them with the wall, if your trinket is down -- and even if it's up, the wall distance is farther than the trinket. Walling and then slowly making your way around the corner to see them is not good because by then they will have flashed or used an ability to get over the wall... the point was you wall and E them in the half-second that they're disoriented/knocked.
This nerf just FEELS bad. If I'm not mistaken Anivia is the slowest immobile mage. She needs the vision. You guys already nerfed her in your mage rework earlier... leave her be. Taking the vision off Trundle's pillar is not as big of a deal for someone like Trundle but it's a HUGE NERF for Anivia. If you are going to nerf her with zero discussion or justification or requests from the community then at least give her a buff to compensate, but it would be easier to just revert this nonsense change.