There's a simple concept:
- Ranged is almost always superior to melee in league due to base stats being too similar.
- Most ranged spells are skillshots.
- The only way to dodge skillshots is by moving out of their way - with mobility.
- Champs with mobility can hit you at their choosing if you have less mobility, while its very hard to figth back. The only way to fight back is with extreme range to never even let them touch you, with mobility of your own, or point-and-click damage (point and click spells, autos).
- Champions with high skillshot dependence, low range and low mobility are thus terrible, because they get hit without being able to hit back.
Without looking at the numbers, Veigar is weaker, because he can no longer counter mobile champions, is short ranged, and immobile.