Actually, rope trick is pretty effective. Not only are you on another plane, but there is simply no way to teleport to your location! Moreover, you give the scrier no clues about your surroundings, assuming you fail the Will save.
Admittedly, rope trick is useful only when "camping" or pausing to plan.
As I see it, scrying (the 4th level spell) is really only useful within the "scry-buff-teleport" combo, as the scry spell has such a short duration. What's the likelihood of the Bad Guys(tm) hearing anything useful over the course of a few minutes per day? A better plan for the Bad Guys(tm) is to gather the strike team, scry on the PCs, then teleport and start the slaughter and mayhem.
For the record, that would probably require a cleric and a wizard, both of at least 9th level. So the tactic is neither cheap nor easy. ...And there are counters, as as already been mentioned. Still, the Bad Guys(tm) should use their best techniques as early as possible...it helps "ramp up" the intensity and believability of the story. You won't regret it!