I don't like my odds for finding a location that's within 24" of my opponent's psykers, out of 24" from my psykers, and not a death trap. May as well just grab the farseer and shove him in the corner with a scoring unit if I'm going to take a global psychic defense at all... and this one synergizes well with aegis, whereas the runic weapon does not. The only case where runic weapons are appreciably better than RoW are against Eldar who get in range of the Rune Priest. And even then, Runic Weapons aren't going to cause psykers to randomly take wounds, RoW can.