anonymous asks: How can Keyleth possibly heal Vax for 12 hp on a 1st lvl healing word of 1d4+wis?

It appears she was also adding her proficiency bonus to the roll. She heals Cassandra with the same level Healing Word earlier in the battle (Ep 33, 1:38:11), says that she rolled a 3, and then gives the 13 HP that Cassandra healed. So, Wis mod (6) plus proficiency bonus (4) plus dice roll (3) equals 13.

The same likely happened with Vax later in the fight (1:54:08).