So lately I've been thinking the need for psyker defence has greatly increased. I mean if you think about it, you wont find a vanilla army without a librarian, or blood angel list with a libby or even mephiston. Most wolf armies run a rune priest, and guard allies for psychic hoods. Even in my eldar list I'm forgoing a second autarch for a farseer just to get runes of warding.
Is having the ability to have psyker defence really that important? I mean armies have been successful without it, such as Stelek's space wolves or my demons, but many competitive players deem it necessary.
So how important is psychic defence in competitive 40k?