I'm playing Yorick like this :D Great Damage Burst, and good surviviability with armor and MR.
I'll tell u right away, if u didnt understand something when i'll tell u something its normal XD and french ;) SOoo Yorick is very OP Champion for a Team, let's explain.

As a Pros :
Good Damage Burst Early, Mid and Late Game.
Can take down ennemie Champion in 2 or 3 sec.
Good Pusher.
Can make team win team fight really quick.


As a Cons :
Feeding the first blood.
Can totaly help other team winning the team fight XD.
Totaly Squishy.
Get focus first.
Mana depend.

For my mastery i take 0/9/21. Armor and MR for start game making me more defencive, and Utility for the Blue buff and mana and health Regen for maximize my casting spell in a row non-stop :) That what make yorick real strong.

Yeah, i'm in a total accord with Phreak for Maximize Slow effect and only 2 life steal because ur slow can save u from dying or get u a fast kill :D Then after i maximize my Q spell for my Sheen, that can make over 1300 Damage one shoot in a Critical Strike :P and this each 3 seconde :D.

Maybe i dont need to explain those spell XD anyone know them, Ghost run its for sure the spell for Yorick, Getting kill or Running Away eazy. Ignite can help to cancel Heal effect, spell vamp or life steal or OP Ult from some Champion ^^ making Yorick a Life Stealer killer :D

Yorick is a Eazy champion :D When fighting with him always make ur W spell (Omen Of Pestilence) First then go right on Your Target making ur Q spell (Omen Of War) then casting ur E Spell (Omen Of Famine. U can always Ult urself right when ur on the target :D making a 2 on 1 fight. When Team fight Yorick can Always make a 6vs5 or a 4vs3 that what a very good Yorick is for, can make more Eazy team fight Winning :D


( You can also Jungle with him with that build, maybe i think XD i dont try it, ill tell u later if that is great :D )