The reason division winners are given a home game (higher seeding) rather than wildcard teams with a better record is to assure that even if a team is in a very tough division that it will not be penalized for it if it wins its division.
Of course, there are situations like this year's Cardinals that are in a horrible division and still won't have a good record, but the reason for it is because some divisions are tougher than others and a team with a 10-6 record may be the best team in the conference but because their division was the toughest in the conference, they have a worse record than a wildcard team.
Now, that being said, I wish they seeded teams based purely on win-loss record before and after each round of the playoffs. If you wanted to be fair, you could seed them based on wins and give teams a bonus win for each wildcard team that is in their division.