Already in Bespin they were incompetent. They allowed the rebels to escape. There wasn't an order to allow them to escape like the DS. Vader demanded the prisoners to be sent to Executor, Calrissian betrayed him and the stormtroopers couldn't stop 3 people from escaping. Vader had to have people to deactivate the Falcon hyperdrive just in case to have any chance of recapturing then
Endor alone would be the only example needed. It was a critical target, the very shield generator that protected the DS were the Emperor himself was stationed. They had the superior numbers and a defensive position. There was no way they could that disaster to happen. Even more "an entire legion of my best troops" as Palpatine had claimed.