Not quite what I meant.
I (and hopefully most people) don't expect a breakdown of the whole fight but I would like to be warned of particularly obscure or dangerous mechanics beforehand - and ask as much.
For example landslide while extremely obvious, is quite a quick cast which is even worse if you have ping, and instantly knocks you out for the rest of the fight - unraisable. Nobody warned me despite my having stated that I was new and having the new player flag, and then I got to sit out the entire fight unable to even see what was going on let alone actually participate and enjoy myself.
Now if we were ALL new that would be fine, they'd almost certainly wipe and we'd learn better.
But because it was 3 high level experienced players they just carried on without me and I missed out. If they had given warning in advance of that mechanic I would have known what to look out for and (hopefully) not get punted out of the arena in the first ~minute or so of the fight!
EDIT: Apparently I reached some kind of post limit
To clarify, I do go in blind but asking for warning of particularly harsh or obscure mechanics. But that's hardly anything at least so far.
The only mechanic I'd really have wanted warning of so far in all the trials and dungeons I've done would be landslide, because of the whole "get hit once and you're out for good" aspect. Doom plates and final sting come close, but they're pretty easy to figure out even if it takes a wipe to realise what's going on.
I like figuring out mechanics but being instantly knocked out of the arena and having the party complete it without even getting to see 95% of the fight is just lame.