Do I think that Darren loved Mia before Chris? No. Absolutely not. No. And I know there are others who claim differently. And I hear that is an angle that may be pushed in the weeks/months ahead. But I am confident they never dated. They met through Chuck and possibly Charlene. Plus one of her friends dated Joe Walker. I think Darren and M were good acquaintances who got along in the company of others. I do not believe they ever dated. It is my understanding, though I cannot verify this, that they wanted Charlene. But Charlene has a soul and morals and said no and M jumped at the opportunity. At the time, it likely looked ideal to D, she lived across the country and had excellent connections within the music industry. Plus they had mutual friends.
As for earlier pics, there is maybe one that i have seen that is actually right after Glee started that I could look at and say maybe. One. But Darren has tons of pics with woman that I see that could be confused for a couple. Again I do not believe they dated.
I do however think Darren had a pseudo beard will he was filing Eastwick. Different woman.