I wouldn't call it predatory - in fact, every significant work test / trial I've done has been paid, which is remarkably progressive! 

However, I empathize with your pain - interviewing for EA jobs is a rigorous and rather impersonal gambit. As far as I know, this is a feature not a bug. It's frustrating but I try to cut them some slack. There are many applicants, EA orgs are almost always short-staffed and they're trying to avoid bias. Most EAs want an EA job but these hiring processes are optimized to test this desire.

Knowing this, I don't bother applying for an EA job unless I truly think that my application can be competitive and that I actually want the job (not a bad heuristic to follow in general).

I understand your frustration, and have myself been in your shoes a few times. I think that many employers/recruiters in EA are aware of these downsides, as I have seen a variety of posts by people discussing this in the past. Additionally, as Samuel points out in a separate comment, many if not all of the work-trials/etc. I've participated in have been compensated, which seems quite reasonable/non-predatory.

Unfortunately, for some positions/situations I don't think there will be any process which satisfies everyone, as they always seem to have downsides. I can especially speak to my experience applying to positions in non-EA think tanks and elsewhere, where I've suspected that most of the interview/review processes are ridiculously subjective or plainly ineffective. Setting aside the process of selecting applicants for proceeding to the interview stage (which I suspect is probably under-resourced/flawed), I've had multiple interviews where I came away thinking "are you seriously telling me that's how they evaluate candidates? That's how they determine if someone is a good researcher? Do they not apply any scrutiny to my claims / are my peers just getting away with total BS here [as I've heard someone imply on at least one occasion]? Do they not want to know any more concrete details about the relevant positions or projects even after I said I could describe them in more detail?" 

Many of the EA-org interviews I've done may not feel "personal," but I'll gladly take objectivity and skill-testing questions over smiles and "tell me your strengths and weaknesses."

That being said, I do sympathize with you, and I do tend to find that it's much more frustrating to be turned down by an EA org after so much effort, but in the end I still think I would prefer to see this kind of deeper testing/evaluation more often.

This should be the low-hanging fruit on transparency; every organization should post the expected hiring process (including work trial duration / compensation) up front.

Sometimes plans change, but any unsuccessful applicant asked to do extra interviews etc. over what was stated should be compensated for them.