Petition the Court of Common Pleas to overturn the sale, revert the property to the former owner, negate the tax sale, refund the high bidder what they paid including fees, recording, etc,, and reinstate all liens and mortgages.b. 

Then get the tax collector to agree that it's disclaimers do not apply to you and overturn the sale.

How much of an average flipper's or developer's ROE is really return on EFFORT for the E component?

There is very little debt on the project so that ROE is very low when coupled with the mismanagement.I sent Steve the name of a securities attorney who does litigation work too to review the operating agreement for the deal to see if he can compel the management to manage the property better.

Since you’re an admitted numbers guy I would focus your attention on maximizing your cash-on-cash return in the short run and your ROE in the long run.

Take a look..http://www.biggerpockets.com/blogs/4579/blog_posts/32645-if-ca-h-is-king-then-leverage-is-god---loans-cash-roe-roi-and-risk

In CA, the trustee can overturn a sale.The OP didn't miss the lis pendens.

The ROE is really low given most of our holdings have almost doubled in value.

The most I’m seeing is 25 years and in 95% of the cases I’m seeing 20 years.Plus, if you’re using a 5/30 73% LTV at (I’m guessing) 4.5% (as you’ll be buying as a non-personal entity) your ROE 7.52%.  

This because you are making more money than the cost of the leverage and your ROE is 11.3% on each of the five rather than 7% on the all-cash deal.