1 hour ago, debiant said:

No, he'd be like Ringo, the backbone of the band, but utterly useless on his own. J/k I love you Ringo. It wouldn't be the only utterly useless card—rare or otherwise—to be found in a deck.

It wouldn't matter at all, since you can always delay playing him until after you used your non-fighting creatures.

Sorry, I read it wrong, I thought you referred to the Horseman of Death. Yeah, what @Admiral Deathrain said.

Have you seen that each of the four horsemen cards are more common than a single Mighty Tiger (deal 4 damage to creature when played). This is a bit off balance, but it could be simply because not too many decks have been added to the compendium to count cards.

Sorry about resurrecting this thread, but this is the first result on google when searching for the OP's question, and this thread does not contain the answer. Here is the list of cards that are limited to 1 per deck according to the below youtube video.

https://www.youtube.com/watch?v=gSXbqpD1paw

Key Charge

Chota Hazri

Lash of Broken Dreams

Burn the Stockpile

Bait and Switch

Key Hammer

Master of ... (you can't have a master of 2 and a master of 3)

Library Access

Wardrummer

Ether Spider

Restringuntus

Replicator

Thanks for the list