First: use the reply button.
Xerath's ult is a circle -- 360 degrees of firing. You would have to zoom out to such an extent that it would be impossible to actually hit anything with his ult, not to mention it sending your frame rate to hell. The reason Jhin has a zoom out is because a) it has a set firing cone, and b) it can be blocked, so he needs to see what's blocking it. Xerath's ult doesn't get blocked by anything.
The vision method of his ult has nothing to do with people not playing Xerath (and btw, his win and play rate are perfectly average), it's that since all his skills are skillshots, you have to put in time into mastering him, as well as until you get good with him, you are very weak to assassins and dive fighters, which are popular in the meta right now