Its very easy to pull off on gravel pit. As soon as one point is capped, the defenders concentrate all their efforts on the second point, which leaves an entire side of C open for engies to play. And since the people respawning get so spread out from those already defending the point, its usually easy pickins one at a time.
As for sticky camping: I say keep it banned. Sure it's easy to not get screwed by it, if you have an organized team. That rarely happens however, since most people don't have mics to warn about it quickly enough, or have voice disabled and can't hear the warnings. So if noone is using a mic, you're entire team is probably gonna get boned at least once just to find out. Not to mention if you're dead you can't communicate to the living people, so you can't have someone come back to help you or send warning to the rest of your team, for upwards of 20 seconds since you're on defense. In the end it could take half a minute or more just to organize your team well enough to break out. Which is ample time to lose a point, and likely the match thereafter.
If this was a private server, I'd say sure to removing that rule. But in a Pub, its just way to frustrating to deal with. One decent demoman can keep a team in their spawn for long enough for a second demo to arrive. Then you're absolutely fucked.