The number of playtesters isn't a mistake; the list that you see there can best be described as team leads, eachof whom have their own playtesting community or group. There are instances of playtest groups of one, but they are few. Usually, the crew from some LGS or some such is involved in the process, but the listed person is the team lead.
There was secondary examination to 2nd Edition as well, a well-considered second review for sanity.
However, if there is a playtest issue, it is likely with the time that team memers get to inspect changes, try them over the board in all circumstances, and implement them for the next iteration of testing. We locally came up with a test plan document that would require approximately 2-3 months for a full testing cycle with a team of 10, using gaming time to get it done, and a whip to enforce a testing schedule. That's a lot! In contrast, the first tier of playtesters get but weeks to evaluate major changes, and, the current fleet breakdown structure was implemented at virtually the very last minute! Very trying circumstances for the playtesters themselves, to say the least.
So, time to consider the changes is the issue.
The result is an inability to rush out product, despite market (and player community) pressure. Triggy, Greg, Wulf, Richard Bax, and the rest of the team that I have temporarily forgotten are doing their level best, and have a lot of people involved --- they just need time to take in all the changes, and that's something that you just don't always get. Business is business and all that.
If there is anything else out there, it is the natural conflict between design vision and game reality. A design lead (here, Matt) has an idea of what he wants the game to be. The playtesters then should experiment, and see if that vision holds, or if clever players come up with tactics, strategy, or loopholes to destroy the vision. Invariably, given enough time (there's that darn word again!), they succeed. The designer is then faced with a choice -- comprimise/scrag the vision, adapt the system to meet the problem, or plunge on regardless in the name of gameplay, fluff, or feel. Balance won't always win out. That is the game producer's call .... who is usually the designer.