Oh, some can be useful, but aside from a few exceptions, they tend to be outmatched by the newer cards
When you have a high % targets bar for entry into the playable realms and the powerful non-linear scaling of these cards a small 5% difference in effect results in a large % difference in potency
Deny the Witch This four-cast instant costs three colors of mana but is very strong with the ability to counter any spell or activity and then force that person to lose some life
Palafin is easy to get hold of, as a Palafin ex box was released shortly after it came out, featuring the ex, regular Palafin, and its preevolution Finizen
But to be clear, the majority of the most powerful cards fall into those colors, so dont think Im forgetting some powerhouse cards along the way