The First

This big fella has a whopping 230K hp and takes a full ops group to take down unless you have higher level characters helping. I've soloed this guy in an older build as a level 30-something but I organized a group of 15 characters between level 13 and 19 and we had a lot of trouble bringing him down.

Be aware that this guy does a knockback which swats the tank away very far so unless you have taunt you might lose aggro at this time. Also since he's a world boss, you're free to revive at the nearby med-clinic if you die and reenter the fray but he does have an enrage timer so if DPS is too low and he isn't going down fast enough he will wipe you and reset. If you're leveling on Dromund Kaas and want to kill this guy, I recommend that you get 16 people at level 15 or higher with a decent mix of tanks, dps and heals but be aware that you all need to be in the same Dromund Kaas instance to fight together so you may need to wait the 30 minute cooldown if anyone recently did group questing and was placed in a different phase.

Killed this guy today on my main and then switched over to my alt that is currently working on Drummond and his respawn seemed to be 2 hours!

It might have a random aspect to it but was for sure 2 hours today!

Drops:

Force Savant's Boots

Advanced Guardian Armoring 5

Downed him with no deaths on first try with 15 players between lvs 15-18 with 1 lv20 as the tank.

I'd recommend 3 healers (2 for tank 1 for raid)
He has 3 abilities that I saw.
1. Light aoe damage to the raid. Nothing to worry about 1 healer can heal it fine.
2. Large knock back on the tank. Try to tank him against a wall or have a Sith Warrior tank so he can use force leap to get right back. It is a temporary agro wipe until tank gets back in range.
3. Enrage Timer. Need to burn him relatively fast. Not sure on the exact time but it's not to bad as we didn't hit it until he was at 5%.

He does not enrage at 10-15% health... He has a 10 minute enrage.

We made three attempts on this boss. First time he enraged at 41%. The second time at 30%. The third time we killed him with no enrage.
He dropped two items:
[Prototype] Sensory Melee D-Power Generator
Phasic Tech D-Shield Generator

seems to be 24h or less, since I can kill him every day and farm gear for my alts :p

I do agree, he does not enrage when his health drops low, but he enraged at 7min 30s for me (just stopped)

Managed to solo as a 36 Sith Juggernaut in decent gear. Enraged after about 10 minutes. Fight took almost 20 minutes. Used two healing potions but only took damage when Smash's Quake wasn't up on him.

Dropped Adv. Reflex Barrel 5, Adv. Commando Armour 5, [Prototype] TD-03A Saboteur Armguards.

Dropped http://www.torhead.com/item/dNyyy2Z for me, along with the already listed http://www.torhead.com/item/aTN88W1.

As for the enrage thing, he enraged about when I hit the half-way mark, I'd say that was about 6-7 minutes in for me.