Not to mention if you get a hide of nemean lion on Guan will make him a nightmare for any AD. His 3rd skill increases his defense so much that it allows Guan to take a lot of auto attacks from any non-super fed AD 1v1 while dishing out quite a bit back himself.
However, with that said, Guan Yu's strengths lies in his ability to go past the enemy front line to isolate an ad carry from the rest of the team fight. Guan Yu differs from other tanks in the fact that he can't 'peel' (protect) his AD carries or mages from other characters such as a ymir, sobek or bacchus can (even hades has better peeling than guan yu).
