Honestly I think it's just a very bad matchup for Irelia.
As a Yorick player I can say your best bet is to attempt to out harass him EXTREMELY early (pre level 3), the hardest times I've had in lane as Yorick have been against players who are exceptionally aggressive right out of the gate. If Yorick is able to stay in lane and farm enough to get tears on his first back (which is quite frankly, not a lot of farm) he will likely be able to sustain himself in lane 1v1 vs. nearly any champ. At this point your best bet is to just play safe and attempt to farm to stay even with his CS (and hope that your AD carry is beating out his, because late game yorick's best attribute is his ult, and if his teams AD carry is getting farmed...team fights get real nasty real fast).
Oh also, yoricks abilities scale off of his AD, but deal magic damage (this includes his E, red ghoul, heals him), building a little bit of MR early can decrease the amount he is healing himself for each time he pops E on you, essentially gimping his sustain.