The Crushbone Orcs is only one of three groups of Orcs on Faydwer.
During the ogre-dwarven war, the dwarves "freed" the Orcs from the Ogres, but only if they would not interfere in the war in favor of both sides. The Orcs were wandering around, without any leader and still the enemy of the dwarves. They were splitting in three different groups, one moved to Rakthok's ridge, the other to the loping plains (which is east of DC) and the third and largest one moved to greater Faydark, lead by Gharol. He gave his clan the name Crushbone Clan.
This is not always true, i've been camping the tiger in Ak'anon zoo. Every time it spawns and i attack, the clockwork standing across will agro and try to kill me. BUT, there is a chasm of some sorts in front of the tiger spawn(to keep it from running away i think) the clockwork will be in it and never comes up.
Yes, these ugly guys see invisible. I was running to Unrest and saw this camp, I stopped to make sure they had no oracles or anything else that might cast See Invisible, before running directly through the camp. I was surrounded and killed because there are 5 or 6 of them and they bash.
These guys only exist in a small 4 spawn camp between Unrest and the canyon to Butcher Block. Follow the east wall. Sometimes an Exiled Legionnaire will spawn at the camp instead and will contain a Blood Stained Note.
I'm fairly certain these guys can see invis. I ran through here in Camo with levitate on, and the chased me halfway around the cauldron before I'd noticed they were there. Oh, and of course they can climb darn near anything, high ledges offer no safety.