C&D taunt kill invisibility is mostly fixed, but some people can still do it with certain exploits.
I should have been more specific about the DR. After the recent patch, many players discovered a bug that let them refill their DR cloak back to 100% without even having to pick up ammo. Someone demonstrated it for me the other day on Sourceop.
As for "not being observant..."
There is literally nothing you can do but try to jump when someone swims under you in the water. It's a ridiculous mechanic made possible by the same bad water physics that brought us the ability to burn people underwater. If they just took out the ability to "jump" in the water (water deep enough to make you swim), all would be well.
I think spy players take these posts too personally. People aren't complaining about people who play spy in a legit way. They're complaining about how sloppily the whole spy class was implemented in TF2.