In Cold Blood

I had no trouble as a merc at 40. I even had torian out to gain affection and did not fall below half, mako I doubt I would have been damaged. CC kren and burn the strong first and after that just move out of the AOE he spawns and jetboost him when he channels lightning at you.

http://www.torhead.com/mission/cvhPZuY/notorious is the next quest in the series.

As merendel said, CC'ing Kren at the start then burning the strong is a big help.

I'm a level 40 mostly Bodyguard Merc, and had Torian out. What I did after the CC & strong burn was to ensure I had 30 stacks of Supercharge up, then I agro'ed Kren before Torian. I did this so I could do the following loose "rotation/sequence" which kept us both very alive:

- Fusion Missle to agro him to me (personal choice, there may be better options)
- Electro Dart > Heroic Moment: On the Trail immediately to keep my health up
- Supercharged Gas to make me kick extra hard with both heals & DPS
- Energy Shield and Kolto Overload as you need it also to keep your health up
- Lots of Tracer Missile on Kren (I made sure to spec high enough into Arsenal to keep this ability)
- Kiting him out of any AOE affects he created + using Jet Boost as merendel suggested
- Plenty of heals on both myself and Torian (or w/e companion you use); this included me using my Reusable Physician Med Unit to heal us both for a nice chunk mid-way through

Either I got very lucky, or my protective tactic is a solid one. Best of luck to all ya'll out there!

Hutta
- Gauntlet - Level 3
- Tools of the Trade - Level 2
- The Last Flight - Level 4
- Big Chief - Level 6
- Settling Accounts - Level 7
- House Cleaning - Level 8
- My Sponsorship - Level 9 [Mako]
- Escaping Hutta - Level 11

Dromund Kaas
- The Hunt on Dromund Kaas - Level 9
- The Huntmaster - Level 9
- A Musty Trail - Level 9
- Family Cleansing - Level 14
- The Spy Game - Level 15
- The Melee - Level 16
- Joy Ride - Level 17 [Spaceship & Start Chapter 1]

Balmorra
- The Balmorran Target - Level 15
- Pirrell's Ambitions - Level 15
- Chaos at the Droid Factory - Level 17
- Down with the Queen - Level 18
- Bait and Switch - Level 19
- Meeting the Admiral - Level 19

Nar Shaddaa
- The Enemy of My Enemy - Level 20
- Economic Boom - Level 21
- The Underdogs - Level 21
- Catching Zees - Level 22
- Industrial Espionage - Level 22
- Professional Courtesy - Level 23
- A Dangerous Auction - Level 24

Tatoonie
- The Tatooine Target - Level 24
- Tracking the Smuggler - Level 24
- Confronting Veeboo - Level 25
- A Barter With The Lady of Pain - Level 26
- Catching A Slippery Eel - Level 28 [Gault]

Alderaan
- The Alderaan Target - Level 28
- Spiking the Punch - Level 28
- Like A Rancor In A Pottery Shop - Level 29
- Silver Tongues - Level 30
- Kingmaker for a Day - Level 31
- Honor Regained - Level 32
- The Mandalorian Killer - Level 32
- Hail the Conquering Hero - Level 32
- Fortune and Glory - Level 32 [End Chapter 1]
- The Heart of Darkness - Level 32

Taris
- A Friendly Wager - Level 32
- A Family Matter - Level 32
- Imperial Bounty - Level 33
- To Walk in Dark Places - Level 33
- Geroya be Haran - Level 34
- Honor or Glory - Level 35 [Torian Cadera]

Quesh
- Endorsement - Level 36

Hoth
- A Dish Served Cold - Level 38
- Cool Reception - Level 38
- Digging His Own Grave - Level 38
- Fire and Ice - Level 39
- In Cold Blood - Level 40 [Blizz]
- Notorious - Level 41
- A Failure to Communicate - Level 41
- Laying Low - Level 41 [End Chapter 2]

Belsavis
- The Ferryman - Level 40
- A Flicker of Hope - Level 41
- Juxtaposition - Level 42
- Mnemonia - Level 43
- Where Few Follow - Level 43
- A Thousand Pardons - Level 43
- No Strings Attached - Level 44 [Skadge]

Voss
- At Arms Length - Level 44
- Nihilistic Mystics - Level 45
- Captive Audience - Level 46
- To Still a Bleeding Heart - Level 47
- Thus, Always, to Tyrants - Level 47

Correlia
- Hostile Takeover - Level 47
- A Queen's Ransom - Level 48
- The Thin Blue Line - Level 49
- Reckoning - Level 50
- Number One with a Bullet - Level 50
- Some People Just Need Killing - Level 50

I managed this as a lvl 37 merc with Torian in 2 tries, first try I messed up and Torian hit Kren after I concussion missiles him so Torian quickly died as I killed off the mob and I nearly killed Kren by myself by running around kiting him for 5 minutes, got him down to 1k HP and ran out of HP packs on my quickbar, which got me killed.

Second try did it right, burned down the other mob very fast and Torian didnt go down till Kren was about half HP, spent 4ish minutes kiting Kren to kill him, was never in any serious danger (used kolto overload twice though). I abused the crap out of jet boost to throw Kren off the starway area, which usually bought me time to sneak in a couple heals.

Vause was a complete joke, fight lasted less than 30 seconds.

Would also point out the gear I and Torian had on wasnt great, only lvl 35 stuff and most of it was green gear, had I been better equipped I would of had absolutely no probs during the quest at lvl 37.

Now waiting 10 mins to try again....thought id come here to see if I was the only one who was having trouble with this...turns out im not! This is ridiculous...I am using Torian and im a level 40 Merc...I get this guy down to under 1k health every single time and its just not in my power to be able to pull this off! This is friggin stupid as all hell!

Update
I figured id try Mako for my last attempt and just have Kren focus on me and incorporate what merendel pointed out, worked out a lot better than I thought, beat up on Kren and got to Vause no problem. Its still a tight fight dont get me wrong, but much easier with Mako (Aff. 6,000) vs Torian (Aff. 1,500). Just dont forget to use Jet Boost!

As you play through storylines of multiple classes, you find a lot of dialog that speaks of "one-on-one" fights that make it clear companions are not allowed, for you or the enemy. Obviously, companions are always there for you. And these fights are always easier than expected when you have your ideal companion out.

I personally believe that BioWare intended to have your companions sit these fights out and tuned the fight to be for you alone (they made it easier), but something changed afterward and they allowed you to keep your companion with you after all. Possibly the issue of 'Well, they can just die and come back with their companion out, and making the game forcibly dismiss the companion was a problem for both the game mechanically and the immersion of the player." I don't know.

Regardless, the Reneget dialog and fights is one of those occurances.