This is my personal build.

The other ultimate has the problem that it is unreliable to get a kill with it.
A good timed "Entomb" is likely to get a kill.

Playstyle:
Frontline, between allies and enemies
Skeletal Swing to slow, even when dead. At level 16 also for heal (e.g. on a minion group)
Drain Hope to put pressure on the lane, or to hunt enemies down, when low
Wraith Walk to flee or hunt (slow) enemies. Don't use it on fast enemies with somewhat live left

Entomb to ensure kills or to divide the enemy team
March of the Black King against a pack of enemies


Level 1:
Reanimation Gives some regeneration, which allows Leoric to stay in action longer. In late game phase, the short death timer will be even shorter.
Level 4:
Hardened Bones for fleeing
Level 7:
Ossein Renewal good tool, when you find yourself in a fight for too long
Level 10:
Entomb is more reliable than March of the Black King
Level 13:
Burning Rage burns enemies (also minions). Very likely you're standing in the middle of the action. A lot! Also especially good against Zagara's creep & Abathur's nests.
Level 16:
Consume Vitality when inside a pack of enemies (e.g. 2 heroes & a minion wave) you heal automatically while attacking them.
Level 20:
Buried Alive It's more likely to get 2 (or 3) kills, when dividing the team with Entomb.