I have finally found the tome after well over 80 rares.
While I'm certainly giddy about it, I'm prepared to have my backside demolished by Kanrethad as I'm a PvP Warlock in 474 iLvl gear, and if it proves impossible, I'll have to accept my fate and wait for the encounter to be nerfed, as my iLvl will only go as high as 476 in full Malevolent.
I simply refuse to do Throne of Thunder LFR just to be able to clear this. This should be a scenario completable by any decent Warlock, even those who dedicate themselves to PvP.