I am a Rank 10 Azmodan with over 100 games played on this character. Azmodan is currently in a funny place: far from being a top tier pick, but still not fully understood. After several games, this is the build that I find to be the most versatile and forgiving in any situation. You will be able to siege and team fight as needed without sacrificing too much in any particular spec.

Following this build, you will turn Azmodan into a true lane bully. His immense HP will be supplemented by your first 3 talent choices. Late game you will get some incredibly debilitating CC that will cripple any team that engages you directly. On top of that, March of Sin will allow you to target healers and DPS in the backline and push them out of the battle allowing your team to cleanup the frontlines.

While this build is not specced for sieging, I find in most games that his (D) + Healing Ward is enough to keep a minion ball strong for a good push. Black Pool also supplements your ability to push a lane once you reach level 10.

The two most commonly chosen Talents in this tier are Taste for Blood and Sieging Wrath. Taste for Blood is fantastic but you really need a companion to help you farm the early game. If you go TfB by yourself, you will spend way too much time in the mid-late game farming minions.

Sieging wrath is generally a bad talent. It forces you to stay out of the frontlines which basically turns every team fight into a 4v5. It's ok for a Siege build (hence its name) but siege builds in general are weak in the current meta.

Healing Ward is the top pick. This talent will allow you to contribute in team fights and will let you keep your minions at full health when you do a siege push.

The choice is between Burn the Weak or Gluttony (everything else is trash). Burn the Weak can be fantastic but I find that Gluttony allows you to farm minions just as well as Burn the Weak and it will provide extra sustain in team fights. Gluttony is the main pick.

First Aid is your go to. Most people take Infernal Globe in this tier. IG is good BUT not vital once you get used to the travel time of a normal globe. The DoT on Infernal globe is also terrible.

First Aid is amazing because Azmodan has the second highest health pool in the game. No tank character has this talent and you are essentially able to act as a tank with an immense health pool. enemies will be demoralized when you use it and realize they still have 35% more azmodan to gun down. You will not die in the mid game with this talent.

Black Pool is an amazing ultimate. An immense damage buff for either yourself or your minions that lasts 10 seconds off of 2 charges. Demonic Invasion is only useful for sieging but black pool will give you both sieging and team fight potential.

March of Sin. At this point Azmodan can tank with a big health pool and can bully healers and dps as he moves towards them with March of Sin. You will clear paths for your team with this ability.

Imposing Presence is the go to. Because of Azmo's gigantic health pool, a full kit of abilities will rarely take you down. Enemies will have to use Auto attacks on you and as soon as they do, they will take 50% DPS loss on auto attacks. Amazing talent vs valla/illidan/zeratul.

Finally we get to fifth circle. Congrats you are now the best tank in the game. A 3 second debuff to Move and Attack speed will SHRED enemy teams apart. Start a team fight by putting down a Black Pool and launching a globe at a cluster of enemies. Follow up with another pool and your death laser and watch as a helpless enemy can't runaway. Beautiful.