The game was ruined before bots deflated the economy. Basically, Bli$$ard set off to make a game where you're essentially working in a sweat-shop several hours a day to try and get items that will either work for your class of choice or sell in the auction house for a decent amount of gold. They have patched out any possible builds that aren't as gear reliant to force an economy where top-level gear is required for Inferno (since, you know, human patience trumps even logic and people will spend cash to get out of annoying spots in video games; it's psychology) . I played the game for over 100 hours, but I'd be lying if I said I enjoyed more than 20 hours of it or so. It's a loot grind game, but the grind is unsatisfying since you have to jump through hoops to do it.
Contrast that to Path of Exile, where the basic premise is the same (the loot grind) but it allows much more character customization and gear isn't king (get a good weapon and that weapon will carry you at least 10 levels or so, especially earlier on).
Basically PoE is a game with a player-driven economy (that is optional). Diablo 3 is an economy with a game (and some people prefer to play the economy than the actual game).
TL;DR: No, bots did not ruin Diablo 3. Diablo 3 was ruined at launch. Damage control in the form of patches have not helped.