And when I get more points than I have ever gotten the very first time I play engineer, does this mean that engineers are really good, that I suck at everything else, that I was lucky, or something completely different?
If you play against a team that doesn't know how to coordinate their ubercharges, bonk'd Scouts or Spy/Pyro sap'n'grill frenzies to get rid of sentry-nests, it's just that easy.
Often only one halfway decent Demoman or a bit more decent Spy could be enough to eliminate a lone sentry and its Engineer.
So they are by no means overpowered, but getting rid of two or three sentries at one place requires some teamplay.
But all in all I think the learning curve for playing a
defensive Engineer is lower than for playing the other classes.
You know where those pesky turtlers set up their sentries from playing other classes. So when you pack a wrench yourself you're most likely use those same spots for putting up your base.