I think you have to keep switching agents, as you get less rep for each mission if you stick with the same one.

My problem is I'm missioning in Caldari space, but one of my 2 characters is Minmatar, so I've got that making my rep gains slower too. I'm flying a T2 fit drake, but I'm a long way from being able to do level 3 missions.

Looks like EVE has it's share of tedious grinding too