Tanks need their %max health damage toned down across the board
This is the specific factor that allows them to either match or out damage bruisers, all without the need to be building any offensive items.
I know than riot has initially employed doing this to stop the anti flashy wet noodle fights in pro play. And it is partially understandable, if they don't have ANY damage threat against each other they will never be able to actually kill each other and will almost always end up in situations of disengaging with each other.
Solution 1: across the board, without increasing any numbers change the %max health to %current health for every pure tank in the game. The fights are less of wet noodle fights, but their damage threat against other non tanks, is quite heavily reduced.
Solution 2: move the %health damage onto their engage skills. for such powerful offensive mechanics IT IS NOT OKAY, that they are on their defensive/range/zoning tools in their kits. this is mostly a call out to the 3 biggest offenders ornn's %health damage is moved onto his dash, maokai's %health damage is moved onto his root, and galio's %health damage is moved onto his dash. Any new potentially made tanks in the future should keep this pattern in their fundamental design