Why doesn't Singed get MR/Lvl?
He's a tank with 125 range, poor hp, atrocious AS, and low base damage. I understand he's a bit wonky to balance with his odd kit, but he's a tank. Shen just got the MR treatment and now Singed needs it. He's hardly ever picked even though it's the tank meta because he isn't even a great tank. His passive gives a tiny amount of hp but it's pretty much implied you're going to go seraph's if you start stacking mana, and that gives no defensive bonuses and usually pushes him towards an AP build with little to no tankiness.
If he needs a rebalance, fine, but I honestly think he'd be fine just having MR/Lvl added without touching anything else. Also I think it'd be fitting to give him 355 MS because his kit revolves around running and juking, but that could be overlooked if he gets this MR buff.