Well, Riot solved that by getting rid of Dominion. ;) But seriously, they were mainly present in the game mode mentioned, and now in Co-Op vs AI, just because they want to level the account and sell it. Doesn't really affect the majority of the population until selling point, and once it's been sold, it's easy to tell a botted account.

Bots has come a long way through Guild Wars where they were basically fancy scripts to inducing AI in the start to becoming chatbots and having bots capable to do elite areas with teams "undetected" (knew the person within the guild, slipped up on guildrun using multiple instances of ghosts in ts). There was also pvp (different bots) bots that can/could do alot more than predetermined patterns.

In pve they became so common that the game economy became completely based off them (without the majority's knowledge).

The intelligence of other bots/programs to give a player an unfair advantage of some sort has also come an awfully long way. One example is the leaps the aimbot took in Halo PC, from being easy to detect even when used by top players to being nearly indetectible (except when priority issues or other bugs/glitches appear).