They also might be in the way of the better perks. Welcome to perk/talent trees.
Its already been said in this thread that these perks are at the END of the destruction perk trees, so it's the other way round.
Well it is a valid concern, a perk that really only does something to an enemy that's already dead anyways for all practical purposes simply isn't that amazing. I'd take a raw 10% damage increase any day over that, especially considering that from all the videos I've seen things in Skyrim die very fast.
Having watched the official demo several times and comparing it to the many 3-hr previews, a few things occured to me. Namely, the character in the demo is at a pretty high level. Look at the skill levels, a lot of the magic skills are right up in to 70s - 80, I think destruction is at 94 or something. Also he has a TON of health! Dragons' fire and bites barely seem to scratch him. It's only his melee skills which are low. Also, that video cuts out time and again, so you only see the start and finish of every fight.