Considering its numerous counters (PC, increased max hp, airborne creatures, eq/black hole, ug/poison rushes, ghostmare and more) I would assume an actual win rate of ~40%. So 3/7 would be reasonable; but still, are you sure you use the deck correctly?
On the deck itself: Those Enchant artefacts wont save you from any deck with PC (and it isnt needed against other decks). I would replace them with shard of bravery (if you have them) or maybe precog or stallish cards.