Thank you for the feedback and suggestions! Adding more lich subraces was on Chris's to-do list, and probably ought to be on my to-do list as well.
Considering that the earliest ever Oberon kill (by far) was
murphy's lich, I'm not sure I buy that liches aren't strong in the early going. He used summons, Magic Missile and Detect Life extensively. It is true, though, that liches are a somewhat problematic race. Evolving into a Demilich (and especially Archlich) gives some extremely powerful innate bonuses; it's very hard to balance something like that, and an extreme XP modifier isn't the most fun way to do it. Chris apparently considered approaching this problem by not giving archliches Mana Storm, but I'm not sure what the justification for that is since monster archliches do get it.