Before we start, I have only used Mordekaiser for a month. I will eventually buy him on my main account and show you the w/l ratio of the AP/Nuke build that I used.

The tank build is a common sequence although I have no rune builds, ever. Mordekaiser is a complete tank/ap ratio build no matter what that you build he will always at least be ap build.

Pros:
He can kill anyone and take tons of damage from almost the whole team
His ult is super powerful against dps and it works even better when you take control of them.
He can solo almost all (I can probably get him with Teemo though]
He's a big pusher with his "E"

Cons:
He's OP and will get targeted a lot
He has not be nerfed in a very long time
Depending on builds Mordekaiser vs Mordekaiser the ap will usually win

The skill sequence I use is very balanced.

The only reason why you would want to start with your shield is if you have spell vamp and you are going to target your mega minions.
People don't understand that his Siphon of Destruction is the best ability he has, as you other builds showing you to start with the shield, it is not very useful.
Always try to get his Ultimate ability he will simply master any dps and increase their attack tons.

Q:
Try to get someone alone it will do more damage then 2 or more people.

W:
Only use if your farming... Really

E:
Use this for farming or multiple enemies or if you have good health regen

Ultimate:
ALWAYS AIM FOR THE DPS

DPS taken as pets = 110 dp 1 second
110 DPS 1 second = tank tower

Statics.
Taking teemo will win the game.
Taking ashe will win the game.
Taking master yi will win the game.
[especially]
Taking vayne [dps] will definitely win the game.

I cannot say much about his Items. This is a very common sequence to pros.