Unless bots are somehow completely eradicated, they'll always infest something. Before Riot removed/reduced custom game XP, bots just kept to themselves. They only spread to Co-op and then PvP after custom games stopped being effective.
As for Dominion, it really needs a more clearly-defined niche in order to thrive. Proper gameplay for the mode takes too much effort for Dom to be suitable for casual players, and yet the mode also lacks any sort of visible ladder for competitive players to fight over. Dom definitely needs more attention from Riot to at least decide what audience the game mode is meant to appeal to. Unfortunately, Riot refuses to do anything unless the map magically generates player attention while in limbo.