I've enjoyed playing with Grim Flayer and I'm looking forward to Dragon's Rage Channeler and Unholy Heat, I think the keyword requires very minimal support beyond just playing good cheap cards. I think of it more like delve or tarmogoyf where some delirium cards are simply generically strong options that a wide array of decks will be happy to play without trying too hard to "do the synergy" and the majority are fairly low power level, low floor rate, low ceiling cards that I think struggle to justify themselves over most generic threats, even in fairly low power cubes.