N6 should never been released in this state, but it is the only way to get enough beta testers to cover as many aspects of the app as possible.
No there are other ways, one of them is to pay beta testers.
Anyway the main problem with Nuendo 6 is not really at this level. The problem is that the test procedures were not clearly defined and / or completes. If they were, we would have seen less evident bugs like the one i did find for the missing automation delta level indicator.
You can have many testers and still miss some bugs if a complete test procedure is not rigorously defined and strictly applied by testers before release.
Obviously defining test procedures is not something programmers like to do, it is a full job for peoples that like to do that. But Nuendo needs this now and i think that the announcement for Nuendo 6.5 prove that SB is now aware of that and for sure you will see that Nuendo 6.5 will be a strong release.