England, who have won the past seven Championships, achieving the Grand Slam six times in doing so, made a perfect start to the 2013 campaign with a 76-0 opening day victory over Scotland.
But back-to-back losses against Ireland - where England suffered a 25-0 shutout - and a 30-20 defeat to France at Twickenham have made it increasingly difficult for them to retain their title.
And No.8 Hunter insists it is not a case of England dropping their standards that has made results more unpredictable, but the ever-increasing level of women's rugby.
"The women's game is really developing now and you've seen that across the RBS 6 Nations this year," said Hunter, who scored two tries in the victory over Scotland.
"Italy beat France, Ireland have beaten us, France have beaten us and it's really becoming competitive and that is very evident on the pitch.
"Sometimes I think you have to be out there and have to lead from the front and realise other nations are catching us up and we can't rest on our laurels.
"Nations are going to overtake us and we really have to put in the hard work all of the time. We've seen in the last two games that we can't just turn up and expect to win."