Cho'Gath - heals like crazy. Dodge Rupture and you'll be fine. You would need Ignite to kill him by yourself.

Nasus - always, does stupid amounts of damage and heals through everything, except when I play him. You can kill him at level 2 if you have Ignite.

Gnar - You can kill him in mini-gnar form once you get a Phage. Before that dodge his Boomerang Throw as much as you can. Tricky ones will auto a minion and then move towards it and then auto it again as they get closer and then they will toss Boomerang Throw out in order to get their third Hyper proc and get you at the same time if you are in range. Matchup would be easier with Ignite.

See a trend? Yorick burns through a **** ton of mana in order to harass his opponents and generally goes Tear of the Goddess to help support spamming. Yorick it strongest when he has as many ghouls out as possible. So that sort of necessitates the use of Teleport. You go back and buy your tear as early as possible to start stacking it and to keep up the ghoul spamming.

But without jungler help you are not going to get ahead in a lot of matchups unless you are running Ignite. However if you do get rolling, you are a beast that is difficult for the enemy team to deal with. But there are even better champs in that category such as Fiora or Darius.