I'm totally with you. It's interesting to hear how subdued the riffs can be over the vocals. What I always appreciated about DT is that they know when not to play. A lot of bands out there, the musicians just want to play. Everyone will constantly play to the full extent of their ability and bombast, and show off what they could do AT ALL TIMES. But with Dream Theater, a lot of the times, during the vocal parts, JP will only play a simple little riff, maybe even something a bit palm-muted or something, and it really lets the music breathe. And it is fun to just hear those quieter riffs and passages for what they are sometimes.
I really love the fact that they do release their instrumental mixes, and it's something I sorely missed from the past 2 albums. But for me, I sing, so another reason I like having the instrumental mixes is so I can sing to them myself. It's fun to sing along with LaBrie, but sometimes it's nice to just sing to nothing but music.