They are actually quite formidable. The problem with Phase Spider is that it got hit by some 'blanket nerfs' because of a rampaging Ancestral Avenger a while back. He still hasn't recovered. Phase Spider was for all intents, and purposes a center piece of the Spider theme. A font runner, a tank, a shocktrooper, a support. Really what ever you needed him to be. With him being far less useful than he used to be, the bgs overall combat capabilities got hindered.