I don't think Earth was as big of a problem as we're giving them credit for. The following is a break down of the Ori episodes. I'm only rewarding "wins" to each side when there's an actual victory and not just avoiding disaster:
Avalon-Origin: Daniel and Vala introduce the Ori to the Milky Way. We'll call this a draw.
Beachhead: The destroy the supergate. Earth Wins.
The Fourth Horsemen: Virus beats up on Earth before they find a cure. Not worth calling a victory.
Ethon: Good-bye Prometheus. Ori Win.
The Scourge: Team beams out in the nick of time. Good thing the bugs were on an unpopulated world, eh? No points either way.
Camelot: Allied forces of good got their asses kicked. Ori Win.
Flesh and Blood: Oh, look. Allied forces of good continue to get their asses handed to them. Ori Win
Counterstrike: Adria gets her ship back and blows up Dakara. Bummer, dude. Ori Win.
The Quest: Yes, they found the means to make a super weapon. But, they didn't ge it completed, and both it and Danny-boy fall into the hands of Adria. Ori Win.
Line in the Sand: Thet hide the village to keep it from destruction. This is another case of avoiding disaster, but to be nice, I'll give credit to earth. Earth Wins.
The Shroud: Yes, they may have destroyed the Ori, but they let several more ships into the galaxy, and disengaged the supergate so more can come at will. Draw.
Dominion: Adria's ascended. Oh, shit son. Ori Win.
Unending: SG1 gets fancy new-fangle toys to play with. Unfortunately, they can't actually play with the toys unless they want to die. Draw.
So, in most semi-direct conflicts, I'm only showing Earth with 2 shown victories that count as actual blows agains the Ori, while the Ori racked up 6 wins that are shown as blows against the good guys. The Tau'ri weren't the threat to the Ori that they were to the Goa'uld, and they certainly weren't as big of a nuisance in the Ori's book.