A lot of it sounds like it's mostly there to serve a different functional purpose in the main game, like giving the spells to other NPCs (like Dragon Priests) or creatures. And most of the other stuff seems crazy OP, or just incomplete. I doubt that Dragonborn Sword actually has any effect to match the description, and the Daedric Greatsword model probably is a placeholder. It probably didn't survive against Miraak's Sword and the Bloodskal Blade.
The Pack Spider was probably removed so that the Dremora Butler would retain it's usefulness. Shame we didn't get Dragon Breath, though I wouldn't be surprised if it was packaged in another DLC. Are you sure it's not just the same as the continuous Fire Breath Shout that Dragons use?
Also, I wouldn't be surprised if someone peeked into the Creation Kit and found incomplete quest data for the Bow of the Stag Prince. Everything about that bow screams incomplete. --- Sometimes I edit my sig so it continues whatever I was posting about.
The Firebreath spell works exactly like the Lightening Storm spell except its a blast of Fire (Like Flames) that is fired. Even has Fire burning all over whereas Lightening Storm has Electricity. --- HOLY ****! What is this? Forged in Gods very flames! Do mine eyes tell me lies? A new Elder Scrolls game? Time is nigh, I must fly, Venture forth on my quest!