These are the heroes I'm comfortable playing in my role in just about any situation (outside of directly being countered by multiple opponents).
These are the heroes with which I'm competent but would prefer to play with some synergies in the team or as direct counters to some opponent.
These are the heroes I'm practicing in free time. I *could* take them in ranked/league play, but only if there was a strong need or obvious reason for one of them specifically. (i.e. specific combos)
Tank / Brusier
These are the tanks or off-laners that I am comfortable playing.
Healer / Support
These are the healers I'm confident to play. I could play other healers in a pinch, but if we need me on heals, I'm comfiest here.