If you mean their theme would have mind related spells to cause effects to enemies, I could see that, though Mesmer already covers that.
If you mean to actually take command of an enemy and perform actions for them, it would be both difficult to implement, and suffer from a huge balance issue with its skills.
I wouldn't care much for PvE, but for PvP, there's a thin line between when a skill is useless, and when a skill is overpowered, and with a tricky thing like 'Mind Control' comes along, it's almost certainly going to be one of the 2.
All of that aside, this is probably too vague for a concept profession.
Yeah, this would be way over powered. If you want to have more "allies" fighting with you just us minions and spirits. Controling the enemy wouldn't work in PvP and would be no fun for the person whos ahveing there character taken control of. Think abotu it, A full team of mind controlers takes complete control of a full other team.
This skill would make america NEVER get favour. Since almost 95% of americans do IWAY in HoH, europe would just use it on the order necro and BAM, bye bye IWAY team.