In most variations they allow you to protect key cards that end up in your graveyard early game until you've established board control and have sufficient mana to deploy Archaeomancer and the like with protection. Clear the Mind also has the potential to protect against mill or MLD strategies as well as being a tool versus other graveyard dependent decks.
For my Esper lists, Devious Cover-Up is replacing Overrule which ends up being slightly better given it's a hard counter. Overrule could occasionally snipe an early spell but in the mid-game was iffy given non-Green decks' lack of ramp. It could just as easily be Dissolve or another 3 mana Cancel. It feels borderline win-more but given the decks reliance on recurring spells it seemed like a possibility. I've also testing Conjurer's Bauble as a means to protect both of them as well as Ghostly Flicker or other key cards that end up in the yard early.
I like both cards but I feel like I'd only want them in decks that aren't running black or green. The amount of recursion available in black makes these pretty unnecessary, or at least Clear the Mind. Green also has enough recursion if you have the Ghostly Flicker endgame that Clear the Mind isn't needed. Devious Cover-Up is solid enough that I'd likely run it anyway in a large percentage of decks regardless of the supporting colors, but I'd only run Clear the Mind if I am really hurting for recursion. What decks have you been running them in besides Merieke?
Since we've last talked, I've decided to try this combo a little more. I just added the pair to my Nevinyrral list that is likely slow as molasses. I also intend to include them in a Lonis, Cryptozoologist turbofog-style deck that I am working on. How has your experience been with them so far @Zombie Shakespeare?
I've enjoyed working with both. They're standard includes for my Ux control lists these days (NOTE for others reading, my lists don't include infinite combos so YMMV). They seem well positioned in your Nevinyrral's list with all the extra sac-card draw. The biggest challenge I ran into initially was wanting to hold the Clear the Mind too long rather than using it earlier to just recycle a few cards.