I'm not sure these should be called "designer drugs" because that makes it sound like people are making and taking them to have specific, desirable effects. That's not the case: in most cases, people don't want to be taking these drugs, they want to be taking the illegal drugs that have "better" effects, but are taking legal or grey-legality drugs because drug prohibition keeps them from taking the drugs they actually want to take, which are better-understood and generally safer.
I'd prefer to call these grey-market substances "research chemicals" because it's a neutral term without the fearmongering associated with "bath salts" or the romanticizing of "designer drugs". And it's honest: these are chemicals that we are researching and should continue to research, to understand both the positive and negative effects these substances have.
It's a dangerous world out there. If you're going to use drugs, please use a test kit. And everyone should obtain and learn how to administer Narcan if you can.