Yeah, I think just a vial and 1 card is kind of weak when crafting is about mixing cards to create other cards. So your suggestion of Vial + 2 cards (1 out-element and 1 in-element) seems okay.
Vial + …

Lightning + Protect Artifact= Quintessence

Shockwave + RoF= UG

Drain Life + Chaos Seed = Liquid Shadow

Plague + Twin Universe= Aflatoxin

Plate Armor + Freeze = Basilisk Blood

Pandemonium + Heal = Antimatter

Fire Bolt + Blessing = Rage Potion

Gravity Pull + Nova = Black Hole

Heal + Momentum = Adrenaline

Holy Light + Thunderstorm? = Luciferin

Sundial + Momentum = Precognition

Freeze + Mutation = Nymph's Tears