Press the Attack and Precision
I was extremely upset to see Press the Attack changed from a keystone that would have benefited many bruisers to a keystone overwhelming slanted towards ADC.
The trees are meant to reflect different playstyles. Sorcery is for casters, domination is for roaming and ganking, resolve is for tanky frontlining, but precision, which is supposed to be for DPS (a play pattern) is forced to pander almost exclusively to ADCs (a champion class). I'd like to see precision return to being a proper DPS tree and not a tree just for ADCs. The Press the Attack changes leave tanky DPS/bruisers without a strong damage keystone and also gates them from the precision tree as a primary because none of the keystone fit. Bruisers are left with phase rush and maybe grasp, but the resolve tree is really undertuned so they'll likely avoid taking resolve as a primary.
I desperately hope that Riot leaves Lethal Tempo and Fleet Footwork for ADCs, and reverts Press the Attack into a keystone for fighters that weave auto attacks and cast abilities together in extended engagements.