What factors do you consider when you decide who gains MR per level and who doesn't? There are some champs in certain roles that do not gain MR per level while others in the same role do. Shen gains no MR per level but other tanks do, Poppy is probably the only fighter that gains no MR per level. Kassadin who functions as an anti mage assassin gains no MR per level even though other assassins have MR growth.
Eventually I think it will be normalized to all melee champions getting MR per level. I have no doubt that Poppy will receive MR/lvl on her rework.
Riot has stated before that certain champions didn't get MR/lvl because of balance, but for some champions, I think it's been hypocritical. Most of the no MR/lvl melee's are old champions who suffer from being old champions when Riot had better reasons for not giving MR/lvl based on the kit the champion possessed. For instance, Shen had a shield and self heal and a global ult. He couldn't be pushed out of lane and he was omnipresent. So they didn't give him MR/lvl. Poppy has a passive that reduces a lot of damage already. She gets free armor as well in her W, so she can build MR early to compensate, and her Ult is so broken it's ridiculous, so they didn't give her MR/lvl. Maokai is like a mix of those two in that he can heal himself with his passive and his Ult can reduce so much damage. Kassadin has a passive that gives 15% reduced magic damage and a shield on his Q. Galio scales off of MR, and that's why he used to not have MR/lvl. Yasuo is interesting as he only has his passive shield and his windwall to protect against any sort of magical damage, yet he doesn't get MR/lvl. Giving MR/lvl on release would have been insane given how overloaded his kit was/is, but I dream of a day when all melee champions have MR/lvl to make it more consistent, because you can find other champions such as Rammus that have free sources of resistances that still have MR/lvl. Lot's of champions have shields that scale WAY better than Shen's (Sion/Nautilus). Gragas has a better self heal than Maokai. And the list goes on.
But I digress.
I did neglect Kayle, but I'm not sure where she stands in terms of Ranged/Melee. She is the most "Hybrid" champion that Riot has made. With 40% CDR, she can be ranged 100% of the time. So I think it's tough to say what to do with her in terms of MR/lvl.
Now some of the champions I mention are in need of some help to make them stronger picks (Shen/Kassadin), whereas some of them are picked very frequently in pro play to great effect (Maokai). The normalization of MR/lvl will be a huge balance problem for the Balance Team to deal with right now. It would be challenging to balance certain champions around it. Maokai is strong right now and giving him MR/lvl would make him too easy of a blind pick as he would fair well against ANY champion. He has a shit ton of CC, he has wave clear, he has a passive heal that let's him stay in lane for a long time and his Ult let's him out-trade lane opponents at any time. Kayle and Kassadin would be problematic as well.
Other champions I think could receive MR/lvl without many problems like Shen or Yasuo. Some changes might need to be made if they become OP again, but if that happens they can take some of the Anti-damage out of their kits.
Poppy will be reworked soon, so I think she will be easier to balance.
I dunno what Riot would say about the MR/lvl debacle but this is my take.
