If you are going to be running suicides regularly once you unlock them, then definitely Diablo. His sig ability is very strong when running suicides, as well as his overall value. If you are still mostly going to be running without suicides (despite having them unlocked) then Doom.
funnily enough, I finished exploring act 8.1 today and pulled a mystic ag again, so both will probably be awakened now lol
Diablo - I'm a suicides 24/7 user and he was my first mystic r4 and second champion after herc to sig 200.Us ouchies users want certain champions; Diablo has to be in the top 5, alongside herc, Omega, Claire and corvus. My r4 auto fights all of ROL and chapters 1 and 2 of uncollected EQ and most lanes in chapter 3.No idea why anyone would awaken doom over Diablo who isn't in the running for top 30 AQ.