I agree that using a flamer, storm bolter or heavy bolter is going to be more effective. Using a horde is one more effective way to allow other members of the kill-team to shine. It's a great point. Getting back to the point I disagree that Librarians are taking over the show - like I said earlier. The primary thing you need to do when you have a overzealous librarian that wants to use powers is make sure you are using the Psychic Phenomena table. It does limit the librarian and creates a great deal of tension.
Also, I have never even had to deal with a high rank librarian. I think the highest we have played was where we were around Rank 3-4. The librarian in our group was already a little bit insane at this point. I think the largest magnitude horde I have put my characters against was 40 but there were other things that they were fighting at the same time.
I wouldn't come up with houserules specfically limiting the Librarian. I personally like to design my encounters in ways create a dynamic encounter… For Example: An orc nob, a few orc boys, half dozen gretchen and a horde of attack squigs can be a nasty encounter and give everyone the opportunity to participate.
I like the idea of using the corruption from Dark Heresy. In Deathwatch, they are pretty much immune to corruption until they hit 100 and hand over their character. There is a malignancy table in Dark Heresy that would work pretty good. I would steer clear of mutations because after all they are space marines and resistant to the taint of corruption. All in all, there should be some measure of corruption occuring to the Librarian when they reach each 10 points.
I also believe that there should be ways to remove corruption that are difficult. But yes, I believe the malignancy table in Dark Heresy should be used.
While I agree on this somewhat, especially if it fits the current adventure/mission - I don't think creating situations that immobilize a character. I really think FFG has done a great job at balancing the characters for a party role. Like we just talked about with the hordes, a devastator is going to be king at taking down hordes (and vehicles).
Also, a Rank 8 Librarian should be very powerful with a lot of tools but they are not that bad. Refering to the very first post in the thread, a Rank 1 or 2 Librarian could never achieve the level of power allowing for 10d10 attacks with 10 attacks a round. It's just not going to happen. The rules are not being used right. I love hearing a Librarian say I want to push…. as a GM it gets me all giddy inside. I am an adversarial GM. I don't play a character - I just run the game and while the PC's are definitely the center of the world as far as my games go - I also make the games so there is a threat of dying and taking risks while rewarding… are going to have consequences.
Like Cryhavok and a few others have said. In some cases, creating unstable warp areas are great but try and always make a positive side so that the player doesn't feel like his Librarian is getting picked on. Examples:
These are just a few examples and I have used things like this before but not to limit psychers… more to add to the general theme of the mission they are on. I have not ran games at high ranks in Deathwatch (although I have had high rank ascended characters in my deathwatch games).