The idea behind a proper Leoric tank build is fully centered around healing/sustain. Leoric is not a conventional tank in the sense that he can withstand an entire team focusing on him BUT he makes up for his shortcomings on that front by being able to single handedly negate almost every tank in the game. There are 2 major areas you need to focus on with this build. If you do so correctly everything else falls into place perfectly depending on what kind of teammates you have.

1) You need to take every opportunity to go after the wizard minions in minion waves to build up your Reanimation. Leoric is at his best only when he is constantly regaining health.

2) You need to prioritize tanks when it comes you using your draining hope ability. Tanks have the biggest health pools and the least options for escapes. High level Leoric play is fully centered on abusing tanks with your draining hope ability.

Although very effective this build is not fail safe. As mentioned above no matter what you can always be focused down if the enemy team goes that route and you have no backline support. Save your wraith walks for worst case scenarios or spots where a long lasting stun is telegraphed (ie butcher charge). Also you almost ALWAYS want to use your Skeletal Swing to slow down targets you plan to use Draining Hope on. The slower they are, the more you leech.