This is a particularly difficult fight to solo.
Felbeard uses ground hazards that drop whenever he uses "Felsmash" and Warlord Kaz'jatar uses an uninterruptible Root, which will keep you stuck in those hazards.
There are also a TON of patrol mobs around.
The trick is that for some lucky reason, Felbeard and Warlord Kaz'jatar can be aggro'd separately, even though they are standing next to each other. They also have a very small aggro radius.
Pop into Protection spec, if you have it, then carefully walk the area taking out each of the patrol mobs, so you will have plenty of room to dodge the Felsmashes.
Use Heroic Throw, from behind, to pull Felbeard first. Make sure that he does not walk though Warlord Kaz'jatar, so he won't be aggro'd as well.
When Eitrigg pulls a "Hunter Pet" and rushes in like an idiot, stand still and wait for Felbeard to come to you. Keep him as far away from Warlord Kaz'jatar as you can, then pound him down while staying out of his Felsmashes.
Once you get credit for killing Felbeard, heal and repair if needed and then repeat the process by using Heroic Throw from behind Warlord Kaz'jatar.
The credit for killing them is also separate, so it's okay to let Felbeard respawn before you have the second credit.