Sure, you can add Kazakus. I'm now trying to collect some dust to craft him, since it would fit in most of the decks I play in Wild. I'm now playing more in this format but was a Standard Player not long ago. I actually recommend you to put Kazakus in this deck, if you have him.
Regarding Loatheb, there are games that he doesn't shine, but there are others as well where he is crucial, mostly against Mages and Priests. You just must be a little smart when playing him. On turn 5 he is excellent for tempo and you're basically tying the hands of any APM mage. Then you can play a Zola, or Brann + Zola to get 2 copies of it, ruining even more the game of these 2 classes against you. You can even be lucky and get him out of raise dead or playing him with Brann on turn 8+. He has saved me a couple of times because of these strategies you can pull off. Regarding Priest, you have to be more perceptive and try not to lose sight of all the spells they have in their hand. Once they have Shadowreaper and a bunch of spells in their hand, Loatheb is also really, really useful.
Thank you for your suggestion! I will consider that 2 cards. I know Demon Wrath is great against aggros, but right know I think my matchups don't justify that choice, but Cascading Disaster is such a great card. I will consider it.