The bots just aren't as good as the players

Sometimes you dont know you want something till you know you dont have it.

Now I want bots to do this.

Bots are not meant to carry you on higher difficulties, and you couldn’t be more wrong, with the right setup they are better than a lot of average public group random players.
Legend is very much doable with bots only.

They are awful

Personally I find that the bots have improved a fair bit as of late. In particular with using range attacks in order to target specials or to free the player(s) from disablers.

They follow you around and get you up. That’s already more than can be said for most pub players.

But they dont get you up most of the time in any hard situation. They tend to ignore downed player if anything else is near. And they kill even skaven slaves too slow, so they will never get you up.