Make Conditioning Less Niche
Conditioning is a Resolve mastery favoring tanks who want to sacrifice early for mid game power. I like the idea but I don't like the execution. it gives 8 armor and 8 magic resist at 10 minutes as well as 5% more of each resist type. It would be better if it gave for example (just throwing numbers out there) 20 Armor and 20 MR with no % scaling. The ones it competes with don't require you to wait 10 minutes (when games usually already are tilted heavily in either direction) but also have the % component. This % resist component makes the mastery needlesly niche. It massively favors champions with built in resist buffs such as Singed or Malphite. This makes the mastery far less useful for people who just want to be tankier at that stage but don't have an OP synergy with it. This means that if you're just an average tanky champion like Nautilus, you are in a sense going to be less favored in the meta because you don't have special synergy with such a mastery.
EDIT: I was wrong. I looked at the champions more and it turns out that flat resists would give even more OP synergies. For example Rammus has a 90% armor scaling on W. Malphite gets no flat armor but has % bonuses. They clearly came up with something more generalized than I did in my 5 minutes of thinking about this. :D