The issue is that Graha would only recover 2 life per combat, which would likely not match the amount of life lost per round
Yiazmat is extremely difficult to defeat in-game, so since you went through all the perils of completing this sidequest, now your opponents have to go through the perils of battling this nearly indestructible ultimate boss
Why it's rare: This card is rare due to its striking drawing of Ursula and the character's popularity within the Into The Inlkands Set and Lorcana TCG
Its a Midrange deck that provides a large number of recourses to mess with your opponents board state and strategies, splashed with Evasive Questing cards like Pongo and Peter Pan, Never Landing
Opponents have to pay life equal to Raubahns power just to target it, and with the right equipment, that cost can get painful fast
It could be used to play fewer of your key cards at four copies because you essentially have an alternate way of getting them