Played 1st game with him w/ Amaranth
Did not go well but I don't believe it was my fault nor did anyone blame me
Either way, need to understand him and be better with him
Decided I will be maining Arthas

Is he a tank or a bruiser?
I self healed with Q and R, took block and still could not tank half as good as Muradin
If I am the only tank on the team, do I still spec double hit trait or 50% more heal?
Is it better to take zombies for heal or dragon? (leaning more towards zombies after playing 2 games)

Arthas is a bruiser.

The dragon is usually better in coordinated fights.

Arthas is a good warrior, but he shouldn't be played without another warrior to tank damage as well. Don't take block at level 1 and make sure you get the self heal at level 7. Take both shield talents later in the game and as far as your ult goes....it just depends on what map you are playing and what team comp you're a part of. If you have an Uther solo healer and the other team has a ton of burst damage you will want to take the zombies to assist him in teamfights and keep yourself up so he can focus on keeping everyone else alive.

If you are on a map like the mines/BoE/Infernal Shrines or something though where there will be a 'boss' shoving down a lane every so often it may be smarter to take sindragosa and disable an entire fort so your boss can survive longer and do more damage.