It all depends on the class and even the spec in some cases. While I am not a new player I have had no problems clearing both wings to the current max. I haven't done anything differently then what a new player would do. I've died once or twice I believe where I did end up pulling to many. And I came close to dying on one boss where my pet died twice. That might be a case where a new player could fail.
It is more about being able to sense what powers might be good to pick. And luck. So a new player might not that aspect. It is just general skill at the game. Last run I was able to get 6 demonic tyrants up at once and had +75% with pets. So I would think even a brand new Warlock could have melted most things with powers like that.
The maw currency also can buy some upgrades that could help but the really helpful ones are later on in rep. But if you have less then 10 powers you are doing it wrong and setting yourself up for failure. I usually get 16+ and if I get the perk that gives me currency when casting dreadstalkers early enough I can easily buy up both vendors.