Perhaps we should do a kind of matrix instead, with two dimensions, power and versatility.

Power: Gamebreaking/Powerful/unable to contribute
Versatility: Everything/versatile/one-dimensional.

The classical tiers would be:
T1: Gamebreaking/everything
T2: Gamebreaking/versatile
T3: Powerful/versatile
T4: powerful/one-dimensional or unable to contribute/versatile
T5/6: unable to contribute/one-dimensional