As a tank you do not need to deal a heck load of damage on your own. The tank is the shield of the team that blocks the incoming attacks on the team while the DPS is the sword that kills it. The healer is the repair team that makes sure all the armor is whole and do not break all of a sudden.

You should always focus on playing your role as good as possibl as the party content will be harder than the solo content by far and for solo content you always have the chokobo helper.