You know what, you're right about
Magus of the Disk,
Planar Cleansing, and
Bontu's Last Reckoning. There are much better options in those colors. I'll add in
Wash Out, but not the others.
In Garruk's Wake is one I've considered removing, but destroying Planeswalkers is becoming increasingly relevant (and it's one-sided).
Hour of Devastation's ability to get around indestructible isn't relevant, because I can't really think of any indestructible creatures with 5 or less toughness that are worth destroying (Keranos and Purphoros are the only ones that come to mind, at which point it's more of a meta-dependent hate piece).
Wildfire used to be on the list until I tried it out. It works well in very specific decks, and it can't be one of the best when it's that specific.