Solo Q tier list is pretty much how hard you can carry by yourself, support isn't a thing by itself. It supports the adc during lane and the whole team afterward. There shouldn't be a solo q support tier list at all as supports can't turn the game around by themselves. Support is totally depended on the team comp and how well they interact with each other, forming combos. A tier C support on this list could be tier A with certain team/adc at clutch composition.