The counter gain seems minuscule at +2/+2 but if you are running a lot of Spirits and Arcanes its basically a free effect
Howling Mine is the grandparent of them all, having seen the light of decks back in Alpha , and it does have an interesting catch that not all later iterations have: You can turn the hugs on and off, as long as you have ways to tap or untap the artifact as needed
This makes Shaymin less of a desperate move to drag the game out longer, and more a way to turn the tide and pull things back
But ultimately, you shape your definition of your identity through the decisions you make
Hen Wen Prophetic Pig works great at filtering, and with a high Willpower for his cost, might get a few tries
One Vandalblast or Farewell, even a Counterspell at the opportune time, which youll be doing nothing but telegraphing the entire game by the way, and your day is wrecked