Maybe, but there just aren't enough situations where this card is better than Arsenic.
IMHO unblockable poison can be very powerful, especially when stacked with Deathstalkers and Eclipse. To be fair I think this card has become a bit UP as the game's changed a bit.
Raised Shade Poison Cloak chance to 10%. (>10 Poison means that more than 1 creature has a chance to be cloaked each turn. E.g. 12 Poison = 100% for one creature to be cloaked + 20% chance for another creature to be cloaked.)
I'm also considering adding a 'trigger' similar to Neurotoxin. Thoughts?