So I've been having some fun supporting Lee Sin with an ADC. Its actually pretty decent. Does anyone think its actually viable in solo ranked que?

Problem: Lee needs gold to have a significant impact on the game.

Solution: Give lee top or jungle (or mid, if you're a pro team) and let him farm.

Heroes like Sona don't need farm to have a significant impact on the game. They can buy aura items, cast their ult, and generally just have a team impact without needing to be ridiculously tanky. Same reason Zyra is a pretty good support - she has two good long disables that she can set, then die and still have fulfilled her role.