I see tank as someone with a main focus on…tanking, meaning main investment in CON, and maining defensive classes (more than 1 circle), such as Peltasta and Rodelero etc… 1 circle in Peltasta for Swash Buckling does not make you a tank but a hybrid at best.
Although with ToS’ current Mob AI and defense mechanics, I guess a full fledged tank is not really needed and actually detrimental, so it’s very niche.
I think I should have added more poll options, like hybrid Tank/DPS for Swordies and hybrid Support/DPS for Wizards/Clerics.
EDIT: New poll with more detailed class roles: http://strawpoll.me/6264802