Reading the title it sounded like Australis is dead or its performance is dead ("post mortem" is Latin for "after death": post (“afterwards”) + mortem, from mors (“death”).)

Reading the article (not carefully, I admit, and using google cache, I can't get the page otherwise), I haven't figured out what the TART stands for. But tl dr seems to be "we make this Australis UX revision, and then the tabs are slow, and we see it on the fastest machines, then we search for causes, then we fix them." Well yes, that's the right thing to do. Can somebody point to something interesting in the article that I missed to recognize?