I'm guessing the present generation of Autobots may have forgotten about what it took to defeat a Decepticon. Starscream for instance can shrug off their best blows and weapons but his weapons are devastating. But then again if they follow the original series story in some parts the Cons are more oriented towards combat so they would be naturally tougher. If that one con (starscream) is so bad imagine what a army of them are like? I wonder how the autobots defeated them in the past.