There's not now and there will never be a perfect solution to this, we live in an imperfect world. Where there is networking, storage, compute and a whole gamut of plumbing from different vendors making it all work, something will break at some stage.
That being said, I remember the last fairly major Azure AD meltdown and it turned out that the bulk of requests went to a Texas DC which fell over. Since then, Microsoft claim to have improved this but remember that underneath the hood, AAD is nothing more than a custom build of ADAM. It's not the same as "conventional" AD and so the usual rules don't apply.
Some people prefer on prem, and that's fine. Some people prefer cloud, that's fine. Pick the appropriate tool for the job, don't just follow dogma.