In my unofficial patch, now under testing, I modified the Skeleton to make it a bit weaker than normally: I removed his Armour spell and exchanged Lightning for Missile and I even think of lowering his Health value. I also reduced the chance to get a Skeleton to 80% instead of 100%. Let me give my opinion.
Shouldn't the skeletons be some kind of "cannon fodder" like the ghost, where they simply act as weak extra creatures? Here, in some occasions, you can get so many of them that Dragons, Bile demons and other strong minions can become useless: the skeletons do all the job. It's especially true when they have the Lightning attack as it's one of the strongest offensive spells, which can cause multiple hits and cannot be reflected, which is not the case for the Missile spell. Similarly, because it's possible to get Skeletons in good numbers, attacking with Missile would reduce considerably the amount of things compared to a lightning bolt. Same goes for the sparks of the Armour spell.
About the health, if we compared the Skeleton to other creatures, he has more health than insects, troll, demon spawn, ghost, warlock, tunneller, thief, archer, wizard, monk, priestess and fairy... How does a bag a bones can get more health than creatures with a skin and muscles? Of course, he's undead, but still... For now, I'm hesitating to alter his health because it would change which heroes are worth becoming a Skeleton, excepted if you're in a level without a Torture Chamber, then it won't matter much.
How about you, now? What do you think of all that? Should the Skeleton be nerfed or not?