deathfire touch is terrible
it is designed to only be really strong on either hybrid champions or nieche cases of casters like malzahar with single target dots in their kit.
on anyone else, this thing deals like 50 to 70 damage over 1.5 seconds by lategame. its especially terrible on casters with long cooldowns and designed around burst.
how does this even compare to a 20% attack speed buff, and 15% lifesteal on a crit, when crit is thrown around like candy on halloween?
considering that this is the only offensive keystone mastery for casters, this thing needs to get looked at.

and this is the only viable keystone option for Vlad. However, it's incredibly underwhelming. Even at 600 AP, this only does 120 damage over 3 seconds on single target (so if I hit my Q), or 60 damage over 1.5 seconds on my aoe abilities. And this would be late, late game. It's very rare that I would ever get that much AP in a game if at all.
all love this as a straight-up ratio boost. urgot hits a 1.35 AD ratio on his q! rumble already has this mastery as a passive on one of his core items!