One thing I'd like is for them to mix up the dungeons a little and let us fight the bosses in any order we want, or take a page from variant dungeons and let us alter the bosses based on things we did just before. We don't need to have the large variety of different outcomes that variant offers, but things like "do this puzzle and the boss becomes easier, don't and you have extra mechanics to face" would be another way to spice up dungeon runs. Could even offer extra rewards for doing the harder version like a second chest, or a unique glamour or minion.
I don't see it happening since we'll largely get the "standard run" variant that everyone expects you to know, but it'd be nice to have a little more variety in the standard dungeons. I don't care for the multiple endings of variants, but at least some changes to standard dungeon runs themselves would be nice.