If you want to get a deal, negotiate with the teams yourself. Say, "I want this much, and no less, but I'll show up to camp on time." It doesn't seem that hard to me.
An agent won't help you get drafted higher, won't make you win more games, and won't make you faster or stronger. They all say they can, but the people who do the drafting don't talk to agents. They talk to coaches, they watch film, they talk to the people who've worked with players. They don't talk to agents.
You've got to have great athletes to win, I don't care who the coach is. You can't win without good athletes but you can lose with them. This is where coaching makes the difference.