When you play Live Xerath, and you root yourself and throw out your Q, people dodge. Everyone on the enemy team attempts to dodge. Even the giant tank dodges because Xerath doesn't care about his 140 magic resist. When Xerath ults, people get the fack out of that blast radius, every blast radius. They run before your overwhelming power. The feeling of power that gives you, even if after they're done dodging your ult they run in and kill you, is what makes Xerath who he is.
When I was playing the reworked Xerath in bots, I hit a Wukong with my Q. He didn't dodge it. He didn't move. At first I thought it was a clone, but i wasn't. It just stood in the blast radius, and it was missing about 15% of its health. Then it charged at me, I stunned it with the rolling stun-ball, and I Qed it again. And W. And then it wasn't stunned anymore and it chased me until I ran under a turret.
Reworked Xerath can't fight tanks. I did much better in that game once I stopped trying to attack them. At one point in that game I landed a q on the enemy adc when I could have landed a q on 3 tanks instead. And I made the right choice. Reworked Xerath isn't an artillery champion. He's a sniper champion, whatever the hell that is.
Tankbusting, being able to force everyone to dodge your attacks, is what makes Xerath who he is. The super-long range simply helped make that aspect more apparent. If you cut rework Xerath's range to a third as far, but gave his abilities 35% magic penetration, he would feel like live Xerath. Far more than the awkward character that's currently inhabiting the PBE servers.