Is Xerath Hard to Play

No, a safe pick. Long range, aoe slow hard to dodge, linear stun, spammable abilities.

On a scale of 1 to firing in the opposite direction, how good are you at aiming skill shots?

Xerath skill shots are easy to hit, the more important question is how good are you with positioning? You have massive range ok your q, decent range on your w and your stun is a direct line to your pointer so hitting the shot shouldnt be that hard but you are practically immobile during your q and w and are rooted during your ult. your positioning and skill to hit max range skill shots is where the difficulty is.

Well, basically ziggs and vel levels of skillshotting

only difficult part of his kit is the ult

Xerath is all about being smarter than your opponent in that you need to predict their moves** A LOT.** His ulti can be very hard to hit long range without vision. His Q's charge slows you and his W has a cast time. Otherwise he has tons of range making him relatively safe.