It's not about beating the team by 70, its about finding the best players and recruiting them.
Recruiting isn't easy, playing the game is. Its much harder to get everyone you want particularly in an online dynasty with friends that you can't just go after 10 guys because thats all you need, right?
Also, regardless of how you do it, by year 5 or 6 you are going to have a team that can dominate a computer, right? if so, you have to create other challenges which in my case is recruiting and putting together the best team available.