The problem for Main last season was even when he wasn't loan striker (in the first half of the season) he only managed 3 league goals. You could see his confidence drain every game that went by.
It was actually a smart move by Robinson, even it was partly forced by circumstances, to start playing him as a lone striker. We were fortunate that for the first time in years we suddenly had a midfield that could score goals. I thought Main did a decent job as far as hold up and linking was concerned, but ultimately, a striker needs to be able to score. In the end, he just ended up not taking the gambles confident strikers take to get into positions where he might score.
I don't necessarily expect a lone striker to have the same return as one with a strike partner, but they need to be able to chip in more than 1 goal every 6 months.
A change of scenery might get his confidence back, but I don't think he'll ever be prolific. Stick him beside a regular goalscorer again and he should make a decent contribution.