This involves the extra downside of using your less optimal weapon for the entirety of your opener. All for an exceedingly meagre crit chance gain on Corruption. While it's not impossible that this might amount to some kind of gain anyway, it certainly won't be anything significant. The odds that Devious Minds will proc during the Wild Magic pre-pot window are only about 50%, so half the time you'd have started with your inoptimal weapon for nothing.Yet, it seems to me that prepulling with Wild Magic + Snapshot Weapon + Tricks of the Trade + (Hope for a Devious Mind) is still the way to go over just snapshotting a Devious Mind.
If rolling it with TotT is an option at all I'd just shift the corruption-rolling focus from DM alone to DM + TotT.
Focus Magic really isn't meant for Affliction Warlocks unless the raid doesn't have many caster DPS, or you simply outgear (or otherwise outplay) everyone else. The 3% gain on Corruption is barely going to be worth the GCD it costs the Mage to apply the FM to someone else most of the time, and the same concern about Devious Minds not proccing in time applies here too.
I'm not sure if I'm clear on your point about Death's Embrace - particularly that 70.8% figure.