There's no way to design a good Seer, you can't buff or nerf him into being all right, he should not exist.
This has nothing to do with the aesthetic of the character and everything to do about game abilities. Wall hack is a terrible idea to spam. Bloodhound was enough, and he was an original character so it isn't like the game became different when he got added. We already have enough direct and soft wall hacks, with everyone from Valkyrie to Fuse (just think about it a second if it isn't apparent why), and other in game things you can do to reveal people. But Seer is not just wall hack, he's mass area sustained wall hack on easy mode.
There are few ability themes that will vault you into the broken area, but in any FPS, there's enough history to show when you are treading in that direction. High mobility abilities, area effect abilities, and so on. But probably the very top of the list, or at least tied at the top, is knowing where your opponent is in any game where shooting first is what most often has you win.
You know Respawn has no interest in deleting characters, and isn't very good at admitting mistakes in general. I don't blame them for not deleting Seer but they could trash his kit and redesign it. I mean, I say that, but then again, they seem to not be able to pay attention to how to fix things well when they do (ahem, the Ranked system), so at this point it's a rock and a hard place.
Therefore I have no complaints on hunting Seer, or playing Seer and going aft (just so that 59 players can enjoy 1 less Seer in their game, it's an act of generosity), or whatever other thing players need to do to make them have less Seer in their game. It's actually necessary to make the game experience better.
