Sorry, we're going to have to let you go...
The words that Khan never wanted to hear.

At the beginning of 6th edition, I simply stopped taking Kor'sarro Khan in my White Scars army lists because of the change to outflank and reserve rules.  Not being able to leave your entire army in reserve (assuming its not all flyers and bikes) and not being able to assault out of reserve made the ability to outflank not nearly as good as it used to be.  In addition to these rules changes, him being over priced made it simply not worth it.

Insert the new space marine codex....
Khan received a price cut (45 points!) and the ability to scout practically your entire army saw a reappearance of Khan into White Scars based army lists.  Massed scouting grav guns and melta guns truly terrified particular builds which were dominating the tournament scene and provided balance to the world.  It was all well and good for 2.5 months then bam..... out of no where the Inquisition codex drops.

Must resist using puns...

At first glance, this would seem to be more of a blessing to marines then anything.  Access to cheap divination, access to cheap scoring units (how about 12 points?), access to Coteaz, or even access to rad and psychochoke grenades (+ honor guard with power axes is pretty nasty).  However, I would like to draw your attention to three things. 

Foremost, the Inquisition supplement are battle brothers to all imperial armies, are allies of convenience to Eldar and Tau, and are desperate allies for Dark Eldar.  Therefore, all of the cool things that the inquisition can do is available to a significant amount of armies which are out there. 

Second, the inquisition introduces a modified quazi ally chart in which they are allies, but don't actually take an ally slot.  So then it is completely possible to have Tau and Eldar tag teaming with a rouge inquisitor leading the way.  Best of all 3 worlds with no downsides...

And third:


Servo Skulls.  Yes Servo Skulls.  You know those dinky little tokens that are worth 3 points, come in groups of three, modify blast and deep strike rules, and prevent infiltration and scout moves?  Yeah those things.  For 9 points + the price of an inquisitor, you can shut down all scout and infiltrate deployments.

So why is this a big deal?  Think about the three points I brought up.  Servo skulls were only available to Grey Knights.  If you wanted them, you had to ally with Grey Knights to take them which costs a significant amount of points to do so.  Therefore, we never really saw pick your favorite army with grey knight allies.  Now?  Inquisitors are available to just about everyone of importance and they no longer take up an ally slot.  Yes, they do take up a quazi ally slot but does not take up a regular ally slot (Tau + Tau, Tau + Eldar, or Tau + Marines with the addition of an inquisitor is possible).  Finally, this can all be done for stupidly cheap with little loss to your competitive builds.

In short, Tau and Eldar (+ ally) now have an effective and cheap way to prevent scout and infiltrate moves, with absolutely no loss to the main list.  For 34 points to completely block your opponent's army?  34 points!  That is nothing.  In addition, you get the benefit of reducing blast and deep strike scatters for your riptides or shadow weavers.

Yes... a 3 point upgrade which is now available to just about everyone is the reason why Khan is no longer welcome.  It will take some time for tournament oriented armies to incorporate this new asset into their lists, but it is going to happen.  Time to adapt with the times!

Sorry Khan, but we are going to have to let you go.  You have been replaced by our new intern: 


Now that Khan is no longer in your armies, you have the points for your own inquisitor and servo skulls.  All of the benefits that I pointed out also benefit you!  Fielding a drop pod army?  Servo Skulls!  Don't want to sacrifice your scouts to block infiltrate and scout moves?  Servo Skulls!  Obsessed with Thunderfire Cannons?  Servo Skulls!  Orbital Bombardments never hitting?  Servo Skulls!  

Changing the game... All of this for 34 points.