Thanks everybody for your comments. It seems as if the majority of the heartburn was around Witch Mountain and Revocation being on the list. I don't hate either one, but I just expected more from each.
I listened to them both again today based on the number of comments made, and I still feel that Witch Mountain was subpar compared to what I had hoped it would be. It was just OK to me.
At first, I was thinking I had fucked up on Revocation (because the album starts out rather strongly), but as I continued to listen I figured out what had turned me off before. The answer actually stems from one of the observations which was made above. The album is more fully developed that their last one, for sure, in that there is more variety and some excellent songwriting going on, but therein lay the problem for me as well. I guess I was just impressed with Revocation in the past with how they could keep up the speed and the heaviness for so long without losing my attention, but on this album, they start to wander around from tech death to thrash to more jazz-influenced, progressive stuff, and to me it seemed a little unfocused. There's nothing wrong with experimentation, it just seems to have taken a bit of the edge off that was such a hallmark of theirs on previous albums - and by the term "edge" I mean brutal heaviness coupled ever so carefully with a perfect level of super-clean precision.
In other words, to me, their previous album was like a perfectly honed attack on my senses, whereas this one is still technically impressive, yet explorative at the same time, so it lacks the punch of the previous one.
It's a bit hard for me to explain, but that's my best effort - which probably means that there's a good chance I'm wrong about what I'm saying...so in the end it may just be a matter of taste.
But yeah, Witch Mountain was kinda bland to me. That one is easy to explain.