You really aren't wrong. Those who play non-duelist agents tend tend to have a significantly harder time escaping ranks. It's just much easier to frag out on a duelist and gain more rating that way especially if you are a really strong duelist. Insta-lock duelist if you give coms and are generally a really strong fragger.
However, if you are just a duelist player because you would go negative otherwise, then DO NOT GO DUELIST because you suffer from mechanical aim and game sense. You are going to hold your team back if you go duelist like that.
Insta-lock agent players have bad rep because they are generally represented by players who can't go positive without playing duelist. It's really sad in that sense and brings massive frustration to anyone that plays.