While it must occupy your active slot to get its healing online, I cant think of many Grass decks in the TCG that wouldnt be better without a lumbering shield that not heals itself every turn, but also packs a punch
Removing counters from this card or other artifacts will give you a ton of colorless mana to play with
The decks in Pauper are not well equipped to handle an onslaught of huge monsters in the developing stages of the game
For one, land destruction is now red mana's domain, not white's, and current MtG cards are designed to not destroy too many lands too easily because that leads to unfun gameplay
Most decks dont need more than five or six lands, so holding the extras ensures you always have some discard fodder for your looters
Simic StOmPy Might Have Been Too Repetitive With Llanowar Elves, Elvish Mystic, and Gilded Goose all at the one, Simic StOmPy could play a hyper-reliable first couple of turns