Swain questions for riot

I'm curious about a few things Riot. I have played more games on swain then any other champ. I will say he's strong as a lane opponent but still has weaknesses. Last hitting is difficult but not impossible. His q acts as a slow but the tether can easily be broken. His E and R are where most of his power is for damage. W just makes sure swain can catch the enemy to unleash a full combo. I don't mind scaling the w snare time as much since late game it will still be back to 2 seconds. I do think the nerf was a bit uncalled for though. Swain overall is balanced. He is not a champ that see's play because of his weakness. He has no wave clear and for that reason alone will never see the light of day in competitive play. He also suffers from extreme mana costs that most other champs besides maybe 1 or two others. ( Anivia + kassadin ). If this nerf goes through can swain be compensated with some base ad to help with last hitting? Or can his ult do bonus damage to minions much like a fiddle sticks dark wind ability to allow some bit of wave clear, still with a cost of ramping mana.

I just have a hard time understanding why swain who is very rarely played. Is nerfed even if by a slight amount when Yas, leesin, and others that are strong, and in my opinion have some what loaded kits compared to other champs don't get nerfs and most likely buffs. Swain was made borderline strong only due to the fact of the new keystone masteries. That's all, yet we also see Yas became extremely strong with the same keystone masteries but no nerfs happened with him or tryn. I think the balance team really should take a step back and look at who they are nerfing and why they are nerfing a champion. The problem should have been solved by fixing the keystone masteries first instead of hitting a balanced champion. I don't think the swain nerf is going to make that big of a change for swain but the anivia nerfs will make a large difference. Just would love to have a detailed explination as to why riot is targeting champs that only a small % of people actually play vs other champs that are in some ways broken and anti-fun to play against in lane.