I think we could say that guard are balanced against marines in tier 1, as long as you don't use Commissars, the Command Squad or Grenade launchers.
Poor old man, he's little more than a speed bump.
Anyway, all guard build. Important part to note, in the end battle the Basilisk only fires three times, all at the new force commander. No damage is done from the Basilisk to the troops, the guardsmen stand up to the heavy bolter and Plasma fire and kill the marines on their own.