I've talked about the Creeping Ooze as well briefly as one of the few cards I have that can only be used in Wild when we get the update on the two formats and making me consider going wild instead of focusing on Modern. I have two of them and maybe I should have sold the other one when the price was high, but I still find it useful for my alt so I don't really regret.
The rest of the cards you mentioned I don't have and have not used in a long time and currently not in my to buy list. I used to have a level 5 Undead Rexx but I only bought him to flip since I got him for very cheap at the time and was able to sell him at a good price.
Have some !PIZZA.
Yeah these are things that need to be considered when purchasing. I believe the Wild format will contain less players than modern and hence the reward pool will probably be more lucrative as the bots may not like having to deal with cards that cause them more losses. So I will be playing wild.