1. Better production. Please. Smaller bands, like Haken (won't be able to say they're smaller for too much longer, but right now it's still true), have consistently put out very good sounding releases, while Dream Theater's albums continue to sound not very good. In 2013 Haken put out a very well-engineered album in
The Mountain; while Dream Theater, with much more experience, on a bigger label, and with presumably a bigger budget, released an album that was brickwalled all to hell. Even the HDTracks version, though not as brickwalled, sounds really muddy and what I would call artificially heavy. Just... I know it's not easy to produce an album that sounds good, but if Haken cares enough and can afford to hire somebody who can do it, I really don't see why DT can't as well.
2. Backing vocals. Not just live, though that's most important, but in studio as well. Remember that from 1997 to 2009, John and Mike did backing vocals in studio, too. Their voices are all over SFAM and equally as prominent (or more so) on albums like SDOIT, SC and BCSL. To me, that lends a more authentic feel than hearing five JLBs everywhere. Plus there are parts that are just better suited to a more "average guy just carrying the tune" tone than JLB's operatic style. For example: "Running forward, falling back" in Full Circle. Mike especially also offered a lot in the way of vocal texture. I don't just mean by providing harsh vocals in songs like ANTR and CM. Some of my favorite vocal parts in DT come from Mike singing either behind or in tandem with James in a way that adds great texture to the music. One example that springs to mind is "Never could have just a part of it, always need more to get by..." in The Root of All Evil. That line sounds great thanks in no small part to Mike's voice. I also appreciate his sort of weird decision to throw in falsettos for texture from time to time. Like in Prophets of War or, of course, The Test That Stumped Them All. I don't mean to say this just about Mike, though. John could very easily do a lot of the same things, but for whatever reason he just doesn't, so this kind of stuff, which I personally find really cool, is missing from ADTOE and DT12.
As for live vocals, this:
Whether or not he's technically singing something is a moot point (and not proven), because the end result is the same. For the last 2 DVDs JP mouthes along to vocals that are clearly not his, and it looks silly.
If he's singing, why not mix it in, or have him dub it himself afterwards? I like his voice, so I want to hear him! I don't care if it's not as good as JLB's backing vocal, and don't expect it to be.
3. Mike Portnoy in general. I accept he's gone and accept that it's for the best for everyone, and like Mike Mangini a lot. But I honestly feel that DT today lacks the presence of a Mike Portnoy whose heart is in it, who gets along with everyone in the band and who perhaps has a better understanding of his role in it. I know this is an impossibility and as I've said I completely accept that and agree that Mangini in the band is better than Portnoy in the band, given how relations are between him and the other band members today and given the fact that his heart is probably not in it. But that's what I feel is missing.