AI is hard and the way they made the AI meant it doesn't properly judge things or pathfind properly. It's pretty competent at healing and so forth. I think you posted a few videos which were not AI failures either, I liked the "tons o' bots" one
and the one where they didn't go through a creshendo - bots don't know how to operate buttons and likely hasn't even got the right pathfinding to move forwards (it was about as dodgy in Left4Dead).
I wish they could be more autonomous - and some Left4Dead2 changes were odd (choices of who to follow mainly), and they should fix the fact they never carry grenades (even to just give to the active players). Oh well it's meant for humans anyway!