Even though I'm an Order man (hides Nagash pamphlet) I have some Destruction friends so I can give a basic sum-up.
1. Yes, they only have a few elites (even in lore they are basically just tribes of orruks who've been battling chaos hordes for so long they almost maxed out their growth) but they're powerhouses and pretty much juggernaut forward. Their weakness is that they aren't versatile and fewer numbers mean holding objectives is tough.
Thus having them as a tribe of bosses that lead more numerous greenskin tribes into battle isn't a bad idea to make up for that.
2. Oh definitely. They'll crush you by charging or grind you to dust and have enough options and "smaller" numbers stuff to not fall into the Ironjaw's problems.
Best way to beat them is to spread the wounds around and make them weaker and weaker until you can take them out wholesale. Focusing on one at a time is like trying to kill a hydra by taking out one head, the rest will tear you apart.
3. Bonesplittaz, tougher than regular Orruks(though the boyz are more versatile), devastating archer fire and with stuff to hunt down and slaughter monsters.
Basically the foil to the Beastclaws who are monster mount heavy and elite to their numerous infantry and anti-monster.
Weakness, they're guys in loin clothes for armor. What do you think?
All in all, fun choices ahead for a future nomad with only wandering and battle/food on his mind.