I don't think "impractical" fits in that context.
Here's the thing, potential assists aren't the character's assets. A character's normals, specials, movement options, and gameplay qualities are their assets. If a weak character is paired with a very complimentary it doesn't suddenly make them a better character they're just a weak character with a good assist. The resulting team may be greater than the sum of its parts, but once one character is isolated the strengths of the character are what come to play. Hence why I believe lists should be based on characters, not teams.