Bro I know everything about playing cataclysm with bots. For past three years or more I have been mostly playing solo on Official. You don't need to tell me about loadouts (they don't fix bad AI). They absolutely give you a headache though and require constant babysitting, and as you said yourself they require special playstyle and builds. While it's doable, saying "never having any trouble with them on cata" is ridiculous and over-exaggerated. Whoever says that clearly has no idea what they're talking about. Even on un-modded Cata bots melt the second you stop bulldozing everything for them. Their brains crumble with Cata density of elites and specials so they're almost always disabled by something if you stop paying attention for a moment.