OK, the one way I could think of doing a 'profession check' would be to have said profession create an item or resource when it is chosen.
i.e. when you choose Path of the Mage, a gamemodifier creates a new item, Badge of the Mage. Quest then looks for Badge of the Mage. Keep in mind that the quest will then 'take away' said badge when the item check is met, so if you plan to 'reuse' the tag, give the Mages multiple badges, or give them another badge after the condition is fulfilled...
The problem with this is keeping players from exchanging said badges with other heroes.
The other option is the resource option (Resource: Mage Class +1 when Mage is chosen), but since these will likely be tracked globally, the game might not look at the stack doing the quest, just if your faction has Mage Class of 1 or higher.
I suppose you could set the resource tag to not global, but I'm not sure how that would work with a hero.