He really loves what he does and it just makes spending time with him extra enjoyable
The two big factors that make Liliana substantially better than Mind Rot and company are that she stays in play and that she can Cruel Edict for -2 loyalty
Part of the value of Toxic Deluge is that life is less risky to pay in powered formats, an extra turn of speed is more valuable, and the tactical applications of Toxic Deluge are quite important
Even if you can't get the second 5/5 dragon with this, it's a good card -- and Red decks will often be able to make this card reach it's ceiling, at which point it's pretty close to unbeatable
Shes basically the ultimate Spike card, with options, resource manipulation, attrition, synergy, an enormous amount of play, and incredible at quieting games down and making them about knowable enough of things that someone very dedicated can actually have a handle on most everything