He was good technically but lacked killer instinct and didn't have much finishing ability. He did destroy Mir, but that was shortly after Mir's motorcycle crash when he was pudgy and not 100%.
Vera had so many disappointing fights where he won many/most striking exchanges but ended up losing due to grappling or getting KO'd (Silva, Couture, Rothwell, Shogun). Jardine beat him by simply being more aggressive and controlling the cage. You'd think Vera would've found exploited Jardine's weak chin but he didn't.