After giving this some more thought, the first issue could very well have been my browser saying "no, sir, no dancin' today". The other issues cannot so easily be blamed on me or my browser.

deleted pages still turn up in RecentChanges

So what's left in this task is "Special:RecentChanges unexpectedly lists deleted pages"? If so, feel free to edit the task summary and task description accordingly. Thanks.

Well, it depends. Are the Wikimedia errors uninteresting because you can't reproduce them? I'll post them again, just in case.

Request from 213.89.11.74 via cp3032 cp3032, Varnish XID 384860270
Error: 503, Backend fetch failed at Thu, 04 May 2017 07:02:47 GMT

and

Request from 213.89.11.74 via cp3041 cp3041, Varnish XID 263225564
Error: 503, Backend fetch failed at Thu, 04 May 2017 07:16:06 GMT

In T164448#3238263, @Nirmos wrote:

Well, it depends. Are the Wikimedia errors uninteresting because you can't reproduce them?

Impossible to say because steps to reproduce are missing. See my previous comment which is awaiting your answer: :)

In T164448#3234428, @Aklapper wrote:

Please see T164059#3224705 and report back if that fixes the problem.

@Nirmos: If "Special:RecentChanges unexpectedly lists deleted pages" still happens, please edit the task summary and task description to describe which single problem this task is about. Thank you!

I haven't been at RecentChanges the last few days, so I can't say for sure, but I'm ok with this being closed as a duplicate of T164059. There seems to be progress there to fix the problem. If I encounter this again after T164059 is solved, I can always open a new bug. Thanks.