Well they had plenty of time during the WC to get around to every player - 16 x 15 = 240 drug tests to carry out over a nearly 8 week period - its really not that hard.
And the difference between a survey and a drug testing programme is that a survey, almost by definition, is meant to represent a snap-shot of opinion from a sample of the population. On the other hand, a drug-testing program is meant to ensure there are no drug cheats in the event. Now maybe universal drug testing is overkill, but only conducting 30 tests over the course of a tournament that was so long is a bit poor imo. I think it would have even been reasonable to say that a member of each team in every match was to be tested. The likelihood that you will be tested has to be so high that players simply aren't prepared to even begin thinking they'll get away with it.
On your broader point re: unfair criticism of the ICC, I agree that they're not the anti-christs that they are often made out to be, and have even done a lot of good over the years, but the fact is they are significantly underperforming is several areas of their stewardship of the game, and it does no-one any favours to try and pretend otherwise. The format of their show-piece tournaments is flawed, and their management of the WC was badly lacking in several respects. They've shown themselves to be essentially impotent on issues like Zimbabwe, and I'd say weak on match-fixing, and drugs. And, as I said, they've done nothing to protect the brand and the players from the ever increasing amount of scheduling - as custodians of the game it should fall to them to do something if all the other parties prove too partisan to do anything. Regardless of their achievements and performances in other areas, that's a rather significant list of things they're not doing well.
The fact that these issues were picked up in a survey of a sample of international players is not at all surprising, because everyone knows all of this. What's lacking is some leadership to change the status quo for the better.