HK-47

Abilities:

• Burst
• Snipe
• Sticky Missiles
• Turret Fire
• Grapple

Activated @ 40% and below:

• Stealth
• Poison Grenade
• Stab

Before we get into the nitty-gritty of this fight you should know the following: if your group's DPS is on the lower end of the scale, you will be hitting enrage timers that will make it nearly impossible to progress through the boss encounters from this point on. We were victim to this several times, our solution was to have our healer contribute to DPS by maintaining DoTs and ignoring turrets (more on that below).

Tank HK where he stands,  you don't really have a choice seeing as trying to LoS him into the elevator room opposite him leads to him spamming Grapple on your group members.

Have the tank move so that HK's back is to the group, this will help reduce Burst damage that happens regularly on whomever has aggro. There have been reports that if a ranged player gets aggro HK will Grapple them into melee range and use this ability as well, we have not seen this happen but then again our ranged can't pull aggro with low DPS (ah, the silver lining). This ability is a channeled AoE cone effect.

Ranged should position themselves leapfrog to each other to easily shake off the sticky missiles. Players can remain stationary until the blue aura under their feet turns red, then it's time to move out of the area. This is where the leapfrog positioning comes in handy, your ranged simply have to move a short distance to the left or right to avoid damaging themselves or others.

Pro tip: If you're in the mood to gain style points and your group has strong DPS you can have the players targeted by sticky missiles run to a shielded turret and drop it there to destroy the shield- you can then DPS it down and remove that element from the fight. My personal suggestion is, don't bother! The damage output of the turrets is inconsequential and unless you have extra DPS to throw around you really can't afford to change focus lest you hit the dreaded enrage timer.

HK will cast Snipe (cannot be interrupted) on a party member which is a pretty hard hitting ability. In our experience it seemed that he used this mostly on the person with second highest threat so if you can predict where this ability is going to land you can anticipate throwing out a force shield to negate some of it if your group has access to that ability. We tried using Guard but this seemed to have no effect- don't waste the globals throwing it around.

At 40% you activate Phase 2. 

HK will go into Stealth mode and stun/sap one of your party members. Group up as soon as he uses Stealth and use AoE abilities to knock him out. If you are grouped up nice and tight this will work consistently. If not, well RIP random sap victim. By knocking him out you avoid the Stab damage (which will nearly always kill the player if they are not topped off and shielded in some way- at least at our gear level) as well as avoiding the Poison Grenade which will be tossed on a random player and should be cleansed as quickly as possible. Once he is knocked out of Stealth go ahead and spread out again, rinse and repeat.

TLDR: Have the tank position HK-47 so that his back is to the group. Using absorb abilities on party members is highly benficial in this encounter. When the blue projected texture appears beneath a player's feet move away from others and then out of it once it changes to red. Ignoring turret fire is fine- perhaps throw Guard on your healer if it helps them. At 40% group up when HK-47 goes into Stealth. AoE once his sap/stun lands on a party member to knock him out. If you are unsuccessful in doing so you will have to deal with increased group damage from Stab and Poison Grenade that could potentially ruin your chances for a successful down.

(Damn even the TLDR is long- srs bizness.)



UPDATE: Bheez put together a video guide to accompany these walls of text, enjoy!
http://welfaregamers.blogspot.com/2012/02/false-empror-hm-guide.html