At Lvl 4 take whichever you prefer, if you can get to Basic Attack a lot, Battleborn's fine, overall in ARAM, I'd suggest Hellforged Armor, 25 armor and 4 seconds longer lifespan for your spawn is fairly good, especially if paired with a later talent, Brutish Vanguard.

At Lvl 7 take whatever you prefer, if you wanna go full dunk build, take Art of Chaos, hitting 2+ heroes should be very doable, personally I am a very aggressive player and also like to take Master of Destruction, the AoE effect is really strong and it succesfully going off on 1 hero will gran the same amount as Art of Chaos, the difference is, you get 4 annihilation stacks PER hero hit, meaning you can get a total of 20 from 1 cast.
A nice trick if you take Master of Destruction, use it on a low health minion near at least 1 hero, if the target dies before the channel is complete, the explosion will happen upon the targets death.

At Lvl 13 take Brutish Vanguard if you took Hellforged Armor at Lvl 7 for a nice little slow. If you took Master of Destruction, I'd advise for Cydea's Kiss, the channel time is reduced by .5 seconds, which doesn't sound like a lot, but does give the enemy that little less time to get out of range, and you healing for 8% of max health on succesfull channel is worth it, with Azmodan's huge health pool. Chain of Command is an okay-ish talent, minion ways usually die too fast, but if you get mercenary camps whenever they spawn it's strong.

At Lvl 4 take whichever talent you feel like, it won't have any impact on your playstyle.

At Lvl 20 take Trample if you wanna have the ability to charge a short distance either for engage or dis-engage, though the animation has a decent wind-up time, so it's not the hardest to see coming, though Azmodans hitbox is fairly big, being an advantage with that ability, if you have 400 stacks or is close, take Pride. You can take Siegebreaker, though overall it's a lacking ultimate, the demons are quickly killed off in ARAM due to AoE and almost constant 5v5 fights.