I personally just assumed it was due to it's less then pleasant art and it's off color effect, knights not withstanding
My current inclination is that Mangara, the Diplomat is great in the 99 of any Mono White deck and some Boros decks too as generic card draw
In these decks it is missing the fourth land drop that is often fatal however it is rare to be throwing back three land hands and it is in finding that 4th land that Oracle shines
Muxus, Goblin Grandee Muxus shows up in Legacy goblin decks and when he first was released, he was a menace to deal with
Ugins Binding, as previously noted, is very intentionally similar to Cyclonic Rift
This keyword allows us to cast a (permanent) spell at a discounted cost from our hand, but it's exiled at the beginning of the following end step