Super ultra good explained solution for your game RIOT, esp. roles
Remove lifesteal
No CC or mobility for burst mages and ADC
All the CC to supports (roots, displaces, stuns)
Tanks can have minor CC but mainly defensive abilities like shields/heals/taunts
No damage to tanks and supports
Make items have significantly less impact on the game or remove altogether - think about a system like in Battlerite
Remove minion last hit mechanic, gold is generated passively (you can still manipulate waves)
Give dive characters no possibility to jump out after a dive - its all in and win or die
Make turrets stronger
Or just keep going your route Riot, so everyone can be an epic 1on1 duel master with sick outplays :) 
