Have you tried any of the 80 instances (HoL, UP, or Occulus)? Those would be a better gauge of if it's possible to do ToC.

Keep in mind the boss lvl difference will greatly affect your hit/miss/resist rate and that the ToC bosses have roughly 166% the HP of the bosses in HoS.

Give it a shot, but remember the difficultly of TOC on regular is supposed to be on part with HOL heroic.