Well then, reopened (and put into state "decision required").
The display issue is obvious. or at least it seems obvious to me, I think if you put it to a vote I would be surprised if less than 8 in 10 users of the website didn't prefer the old method.
This is completely non-controversial and was always planned, you can find it already mentioned in the comments on MBS-1377.
As to the editing issue, now there is usually 2 or 3 times as many "entries" when editing and it is a lot more confusing and time consuming to add the membership information.
How so? As you yourself noticed, you can still make your edit with multiple instrument attributes in the exact same way as before. When the edit is submitted, the server takes care to split the relationship automatically. So I don't see how this can be more work than before.
as an aside I am very angry with the current trend to make advanced editing much harder and more time consuming than it was before, ...
Actually, the objective is the opposite, and I think it is achieved, in general. The grand plan is to have fewer page loads by combining edit pages. E.g., previously, when you wanted to add a dozen relationships to an artist, you had to load an "add relationship" page, edit, submit, load another "add relationship" page, edit, submit, load ... Now you can add the dozen on one page and submit in one go.
For the case where you really only want to add one thing as opposed to a dozen, it may be slightly slower because the one page load is heavier. However, developer time is limited as well, and when there are two separate ways to do something, that's two places that may have bugs, be out of sync with each other, etc.; so continuing to support "the old way" has quite a cost, too.
I often have the feeling that people who complain about new obstacles to editing may not be using the best tools. There may be a shortcut or a feature that would save them a lot of time, but that they aren't aware of. An excellent example: A few days ago, an editor (from the "top editors" list) complained on IRC in passing about how difficult it was to add a relationship to a certain entity that wasn't easy to search for in the relationship dialog, and how much easier it had been before the "Use in a relationship" link was removed, etc. And someone asked, You know that you can just paste the URL for that entity into the dialog, don't you? - Well, that was that problem solved; and I bet using "Use in a relationship" had been much slower.
However, solving workflow problems like that would require that people ask on IRC or in the forums, "I'm doing lots of such-and-such editing in such-and-such a way, and it's unwieldy and tedious, is there perhaps an easier and faster way to do this?" Then either they could be shown an easier way, via a userscript perhaps, or people could start thinking about improvements to the editing interface. But that doesn't happen often enough. Instead, tickets pop up saying "Your new feature is a bug! It's horrible! It must be undone immediately!" (e.g., MBS-7501, MBS-7564, this one), which generally isn't the type of message that is well received.
Regarding the other things you mentioned:
... this is one bad example, artist disambiguation is even worse, where you used to be able to split out an artists' credits from that artist's page instead of having to go to each individual release or recording to fix, an effort that at least triples the time taken to fix artist disambiguation
I'm not sure I understand here. Your description is not completely clear, but it sounds like editing an artist credit (e.g. if there are a number of releases/tracks/whatever using the artist credit "John A. Doe" and some others of the same artist using the artist credit "John B. Doe", but they are actually different persons, you could change all "John B. Doe"s to be a different artist). But that feature hasn't been removed or touched at all, nor anything related that I am aware of.
Anyone who enters membership information at least semi-regularly will save their progress after a half-dozen ARs (I wish it wasn't so but the site is unreliable enough that just one 504 after a few hours of work will drive someone crazy and they will never again do a big project like that without saving progress a half-dozen ARs at a time).
That's unnecessary work, really. When the site has had a hiccough, just click reload on the error page (you may have to confirm to the browser that you really want to re-post). Nothing will be lost.
We just discussed this ticket in the dev meeting:
http://chatlogs.musicbrainz.org/musicbrainz-devel/2014/2014-06/2014-06-23.html#T19-19-00-944659
And we feel that this ticket isn't clear and/or is conflating issues. If you can succinctly state an issue related to this ticket, please open a new ticket. Please DO NOT RE-OPEN this ticket.
Thanks!