The good news is, that ability is good on lots of board states
1 in 8 Murders at Karlov Manor Play Boosters (12.5%) features a card from Special Guests or The List instead of the seventh common card
Seedglaive Mentor One generic, one red, one white creature Mouse Soldier 3/2 Uncommon Vigilance, haste Valiant Whenever Seedglaive Mentor becomes the target of a spell or ability you control for the first time each turn, put a +1/+1 counter on it
Modern Horizons Two, while wildly successful, has lost its throne to the recent Lord of the Rings expansion
Prereleases are great because the set is totally new, the footing is fairly equal as everybody plays with the set for the very first time, and you're all just relaxing and having fun exploring the new cards
Its a perfect bridge piece for decks that want both mana and card advantage