Because of this effect Psykers are obligatory in virtually ALL armies now. Until codices start coming out with ways to give you warp charge during your opponents psychic phase or to give bonuses to deny the witch rolls without having psykers, the only reliable defense in this phase is to posses psykers of your own.
So now to get to the point of the post. Breaking the psychic phase. Really this is for all the imperial armies, however since nothing in the allies matrix prevents sharing of Warp Charge, it is usable to an extent by all factions.
|Nobody Expects Them|
Now the basic inquisitor is 25 points, and another 30 to be a Mastery Level 1 psyker with 2 powers. Now these powers don't really matter, because if you are doing this you should take a Mastery Level 4 psyker as your primary detachment HQ and pick powers you want. So what you are buying with the Inquisitor is a 55 point warp charge. Basically a capacitor.
So taking 5 Psychic Inquisitors with nothing extra would cost 275 points, which isn't cheap, but it brings valuable defense to likely all your Troops and then some, and stabilizes your warp charge pool to at least 6 (5+1 on d6 roll of a 1). Add on any other psykers in your primary list and you are looking at a really good pool for both Offense and Defense. This is not even mentioning any of the specialized wargear that Inquisitors can take.