Maybe (probably) I'm missing something, but I don't understand why you'd want this effect on a Leyline, since you can't use it in the early turns of the game. At best you can spend turns 1 and 2 ramping and then cheat out one expensive spell on turn 3, and maybe that spell is some Eldrazi or other, but is that really a better plan than the existing Sneak Attack or Goryo's Vengeance decks?
I agree, this feels like the worst of the leylines shown so far this set. Does literally nothing until maybe turn 3 or 4, depending on format, and hitting WUBRG is fairly difficult in Standard, Pioneer, and Pauper. It's unusable in Mono-G Commander decks due to color identity.
There's a reason Jodah, Archmage Eternal isn't a factor in competitive formats.
