Yes! I hate the “at my earliest convenience” for the same reason – it comes across as “I’ll do it when I feel like it”. I would only use that phrase at work in terms of someone else (ie “at YOUR earliest convenience”).
That’s just sloppy. We always check who will be available, because usually someone is. We also have a service address, and usually use that for OOO–messages. Then the ones working are responsible for those messages. That said, in my branch nobody seriously awaits an answer in July, but I’m in academica.

I don’t know what to say these days – I’m still working from home so “out of the office” doesn’t sound right any more, but ‘off work’ seems like too much? I’m probably way overthinking it but I’ve felt stuck every time I need to write one lately.
My OOO is almost always “I’m out of the office and will be returning on x date.” My email sig has instructions along the lines of “for questions on x, email this list” for a couple of the more common areas people would contact me about that might need an urgent reply (as the lists go to more than just me, obviously), but most people have finally figured out to contact those lists to start with, anyway. If I were in the middle of a project or something that needed to be moved along in my absence, the project teams usually know when we’re out, but I’d put a back up in that case, if needed, but generally there’s not much to be gained by a longer OOO from me.