Cant really say anything on the Imperial Guard since I don't play them, but seems pretty solid overall. You have a nice mix of armor, horde, air and everything inbetween.
Do give your librarian a Nemesis hammer, though, it costs just as much as the meltabombs. 2 strength 8 (10 with hammerhand from the terminators) are better than one, even if you have armorbane.
Sure, its only Initiative 1 which can suck in 1v1s, but your Librarian shouldn't be in challenges in the first place.
Also, if you can, get the dreadknight a hammer or a sword, its 5 points for concussive and force, or 10 for mastercrafted and force, and makes it exponentially mor terrifingy against monstrous creatures.