Muradin is a tank hero with

A ranged stun:


An area slow:


An escape/engage jump:


That set makes Muradin a very nice tank overall, but is an interesting set for a split pusher sieger.

In the first levels you should stay back, avoiding fights and farm your Perfect Storm
It is a good thing to keep minions away from your tower so it won't deplet its ammo resources but your main focus here is to stack that Perfect Storm.

The Sledgehammer will give you a massive boost to defeat mercenaries quickly. If your team is well organized you should look for opens into merc camps, as you can contribute with a lot of damage while tanking. You will be even better when you get the "Piercing Bolt", mainly on siege camps.

At around mid game your Stormbolt should be doing considerable damage and allowing neat escapes while you stun 2 foes and jump away.

After your third talent you should be ready for some split pushing, even though your next talents will make you even better at it. The idea when split pushing is to avoid fights. You are there to impose such a threat that the enemy needs 2 guys to even have a chance to get you. It is also better to split push the lane on the opposite side of objectives. In a lot of maps its the top lane.
The idea is to tank and clear minion waves with your Thunderclap while you throw your Stormbolt into enemy towers. If you are left unattended you should be able to put down one enemy tier easily.
You should have an eye into the map at all times. observation towers and drones can help a lot here but are not strictly necessary. When you see an enemy approaching you should analyze the situation:

Situation 1:
The enemy is alone and can't stop you.
In this situation you should keep an eye for any others that may join, while keeping hitting the enemy towers.

Situation 2:
The enemy is alone and can stop and/or kill you.
You should run back. Maybe come back with a few mercs, maybe push another lane, maybe join a teamfight before the enemy realize you are gone.

Situation 3:
Two or more enemies ganking.
Now that is the bad situation, and that is what can differ you from an average Muradin Sieger. Usually you just run back and try to let at least one of them get close. Also try to get near a wall that you can jump through. You should be able to tank a few hits, throw your slow and jump off the wall. Use your ultimate if necessary. You can recall, push another lane (your health regen is huge) or join a teamfight. Also, if the other team is moving more than one person to the other side of the objectives, your team should be able to have some advantage on that.

And that's it. The main idea is:

If they don't come, you destroy their defenses.
If they do come, you kill them.
If you can't kill them, you stall them.
If you can't stall them, you run away and you just took their team away from a map objective.

Your teamfight is pretty much the same as a tank Muradin, as you will still be very tanky, with the difference of a big damage boost on your Stormbolt
You will want to hit the Stormbolt on the enemy damage dealers, and try to get more than one if possible. Always try to get, besides a hero, another hero, a mercenary or a building. Try not to jump in too early as before you have Spell Shield you can be bursted.
A nice way to give your team an advantage is to Dwarf Toss and Stormbolt one or two enemies, get nearby and Thunderclap and start running back while being focused, maybe popping Avatar to help you survive. Chances are that your team will get a nice advantage this way. Also, you should be able to throw another Stormbolt before getting away which should give another double stun.

This build should work fine. Another thing that is intersting about split pushers is that your team tend to get more experience as there is always at least 2 lanes with heroes in. The bad thing about it is that your team needs to understand how split pushing works. They should never go all in on 4 vs 5 fights. Just contest the objectives as much as possible while you keep the pressure on your lane.
I haven't found any good variations for this build. If you change anything and it works better please let me know!