If you mean win rate on the Versus ladder:
I'm quite happy if I have a deck with a win rate of like 65 %. If I notice it's more like 50 %, then it's not a deck I should take to a tournament, because you should have an above average win rate on the Versus ladder I guess. But I don't think you can expect to have a win rate of 80 %. But remember most tournaments have best of 3, so with a win rate of 65 % you should be able to win 2 of 3 games quite a lot.
However, there are a lot of 'strange decks' (not meta) which you will face on the Versus ladder. That might change your score. Sometimes you will face 'easy wins', but I also played and lost against decks I think I'll never play against IRL.
And don't trust your win percentage unless you played a lot of games already with it (like 50 - 100 minimum). Otherwise you can't really tell, I had a win streak of 11 once, but that doesn't necessarily mean I'll win the next tournament with it (which I indeed did not
)