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Prelude: this isnt a tactica or info page. this is my personal experience and I just wanted it to share it with some of the non believers of the power of purgations.
I have had terrific luck with these squads. I usually try to field one for approx every 1k points I play. Now I know what your all thinking... "Psycannons? this guy is crazy.... They are completely bunk! they take up way to many points (315 to be exact) and have little to no heavy armour killing capacity and they also take up a slot for a possible LR equivalent killer. i.e. a LR or dreaednaught." Now all this is completely true. They are a giant point sink, a sqaud of 5 costing more than a sqaud of 10 PAGKs (wow, ive never thought about it that way...) 315 (in order to get around the whole "you may not equip GK in PA with any waepon other than what they are equipped with, i give my justicar artificer armour and a psycannon. This way, he keeps his str 6 power weapon and has a psycannon, but comes out to 95 pts, OUCH!) to 275. They cant do anything to armor 13 or 14, and nothing reliably to armour 12. And they do take up a heavy support choice. HOWEVER, I have found this squad to be one of my armies biggest strengths ( i run a pure GK force). One of these squads will reliably pick apart a lightly armoured foot slogging group. (little nids, eldar, zoanthorpe *my favourite thing to kill*, guardsmen, DE, orks), two squads become a hammer to bring down on MEQ. 30 str 6 shots. and three sqauds, become a points and click of doom. oh, hello Abbadon, wait, goodbye. Squad of ten terminators deepstriking, not anymore. Carnifex or hive tyrant, you are the weakest link, goodbye. (everything mentions above, i have actually killed with my psycannons, im not just guessing what would happen). Now yes, with 3 sqauds of them that is 945 (if you've been doing the math) and they probably will not make up they're points in kills, but it is the effect on the morale of your enemy, and the devastating blow of having lost an entire sqaud in one round of shooting, to constantly keep him on his toes and trying to make up for that hole in his line. That sqaud of genestelers he was counting on having assault your termies, not there anymore, he has to find something else to counter them. The squad of banshees that were holding the objective, gone. three of his six DE raiders have just been shot out of the sky on the first turn. Sorry bud. With these three squads, whle almost never making up their points value, you constantly wrongfoot your enemy and make him REact and leave you free to ACT. Now after a turn or two, or against a regular opponenet, they become a number on target. And there isn't really much protecting them other than the shourding. The artificer armor is good for those stray AP3 shots that come their way, but they will occasionally die. However, they also serve a purpose in this. They leave the rest of your army free to do as i pleases. In an annihilation game, those sqauds are only 3 kill points. now with only 5 they are relativley easy to knock out with concentrated shooting, but remember, deploy them as far back as possible and keep them in cover if you can. If you play them safe and to kill or disable entire squads, they will almost never fail you. I know this has been long and rambling, and based on alot of personal experience, but i just wanted to say, give them a chance.
If I want Psycannons, I prefer them to be able to score as well. Two in a squad of 5 do pretty well. if you need a third, get an elite Inquisitor w/psycannon. then you still score, and are throwing 9 S6 shots.
I still prefer two squads of Psycannon troops to one squad of 4 in a non-scoring unit.
I prefer an Inquisitor's Dakka squad over Psycannon purgation squad. with a plasma cannon, it make termies scared.
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I only really use this squad if i am up against a Chaos army (advanced warning)
OR maybe if i am up against a necron force that will have a nightbringer (just to mess with him)
But very seldom...
They are not troops, their cost is higher they tend to have to be static..which is not great...and you need numbers in the squad to keep the psycannons safe..so a bit of a point sink.
I used them in 2 games when I first started DH. They rocked the first game but the person I played next saw what they did and promptly bassied them to death. Then I realized that (as stated above) 2 PAGK squads with either none or 2 special weapons is VERY much prefariable to a purg squad. This was in 4th ed by the way. With 5th ed bringing scoring units and tougher tanks I simply cant justify dropping a Land Raider for a equally costly unit. My LR not only kills stuff but also keeps my PAGKs alive longer in a nice AV14 shell, thats how it makes its points back for me.
Perhaps when they introduce an anti tank weapon option for GKs or get rid of the outrageous cost of Psycannons (we LOSE a st6 weapon and a SB for petes sake!) I may take a dedicated 'devastator' squad. Untill then, no dice.
I hear and I forget, I see and I remember, I do and I understand
Success is the ability to go from failure to failure without losing your enthusiasm.
i must agree with the above comment.
however i will say this, four psycannons is good. 315 worth i dont know, but they are good.