1) Get rid of the 3 min respawn timer on the ???'s for ZNMS. This adds a huge amount of time to anyone who goes out there with more than 1 person, and when 80% of your time doing znms is just standing around waiting for the ??? to respawn, it kinda sucks.
2) Addendum to #1: Consider making ZNM pops and trophies ex only instead of rare/ex. This would allow a solo-er to pop more than 1 at a time and save loaaaaaaaaaads of time running around.
2) Get rid of the 6 person requirement for Einherjar. Even with how easy Einherjar is, not having a 10 min timer with less than 6 people would be nice. (Especially for anyone wanting to do Odin).[And yes - I KNOW ein isn't hard. I personally haven't had a problem with the time limit in ages, but I'm sure it'd benefit a lot of other people]
3) Tinnin: get rid of or change the mechanics where he can't die until all his heads are popped. At the current level/ilvl, he's dies really fast, and sitting there meleeing him at 1% for 10 minutes is a drag.
4) Consider adding HP's near/around where some znm ???'s are. We have them for pretty much everything else in game now, and it'd certainly be nice for some annoyingly out of the way znms to get to like Nuhn and Ex Lamia.
5) Up the 10 day/limit on handing in plates to Sanraku or remove it completely.
With the game on the way out I'm sure a lot of people have mythics they'd like to finish up as a long time goal. There's a lot of small changes you could make that'd make acquiring mythics a lot less annoying but doesn't really change the difficulty level involved.