Ivo Bellin Salarin, I am attaching a sample ordered test result from VS2015 (same schema as VS2010) for your re-consideration on this issue.
Additionally, I am attaching an XSL document, mstest-ordered-to-flat, which will "flatten" the TestEntries node into a non-hierarchal collection of TestEntry nodes.
This XSL file will also delete the OrderedTest node from the TestDefinitions section. In doing so, the Jenkins plugin correctly reports the number of executed tests (because the definition entry is missing for the ordered test).
As a bonus, if you apply this XSL transformation on a standard (non-ordered) TRX file, it will leave the file unchanged. I have tested both ordered and regular test results against version 0.19 of the MSTest plugin and it successfully processes the files.
This technique is preferred over the attached mstest-to-junit XSL file, because it preserves much more of the data, such as console output.
I am not a java-coder so cannot contribute directly, but perhaps the plugin could (optionally) apply this transformation on any or all TRX files before further processing.