Your analysis is correct but you're coming to the wrong conclusions.

It's clear that going in, Marissa needed to fire a lot of Yahoo employees, she just needed to find a way to do that and she found two: 1) revoke remote privileges and 2) stack ranking.

Once she is satisfied that she has gotten rid of all the underperformers, she will most likely cancel these two policies.

And in the meantime, Yahoo is offering top dollars to hire new blood (ideally coming from Google).

I don't see how firing underperformers and other dead weight is evidence of a lack of long-term strategy. To me that sounds like a good first step in a long-term solution of making Yahoo! once again a place that talented people work.