I don't think it was. There was at least a dichotomy between "Mike" and "John" influences before, where you could basically tell who wrote a song before even looking at the linear notes. There were also your occasionally influences from the other guys. Mike stepping away doesn't seem to have led to the other guys writing more, it's just led to double the JP filling the void. Hence me feeling like the sound has become more homogenous.
Are you talking about lyrics or music? If you are just addressing lyrics then I guess I can see your point. John and Mike had been the two main lyricists on recent albums before MP's departure so that dynamic has been different over the last two albums, but if your addressing the music with your comment then I'm a little confused. Its been widely discussed here that for the most part, MP's contributions to the music included composing drum parts (obviously) and simply helping to work with arrangement ideas.
So on SC and BC&SL, JP and JR were still the real driving creative force of the band, muscially creating the riffs, chord progressions, melodies, etc... for the most part. That hasn't really changed with MP's departure, JP and JR still fill that role in the band.
I'm... not in the least sure that you can say that is true outright. Certainly JP and JR are responsible for writing a vast majority of the music, but I'm not at all sure that you can limit Mike's contributions to writing drum parts and "helping to work with arrangement ideas." I think Mike was responsible, far more than anyone aside from maybe Jordan, with coming up with the outside-the-box, outside of the normal direction of the band ideas that we used to see all the time from them. Like them or not, songs like Never Enough and ideas like the fan vocals of Prophets of War, the growled section of A Nightmare to Remember and the three-part harmonies that drench
Black Clouds & Silver Linings were all outside the box and are probably mostly attributable to Mike Portnoy. And those are the kind of things that I love from Dream Theater. I hesitate to be exacting in my remarks because I think the music on the last two albums is very good, safe as it is, but I do think I'd probably rather hear DT11 in 3 years with Mike Portnoy as co-producer than have ADTOE and DT12. This is even while my #1 is Breaking All Illusions. I am nearly that confident that they would have topped BAI with MP in the band (to say nothing of: Jordan/John would probably have written most of what I liked in BAI anyway, and JMX had already planned to return to lyric-writing regardless of whether or not Mike left the band).
I say none of this to slight MM or JP, or to criticize the band for refusing to take a hiatus. I understand why they had to do what they did, and I think they made the right choice. And I think Mike Mangini is an incredible drummer and great fit for Dream Theater. I just miss very much what Mike Portnoy brought to the band.
But when the homogeneousness was oozing with MP's controlling stamp all over it, that was alright? The song quality over the last two releases has improved drastically as compared to Systematic Chaos and BC & SL.
A couple of things: First, I think we should call into question the notion that Mike is as controlling as people claim he is. I mean, it's documented that he had personal issues with John Myung and James, and Mike himself has admitted to having controlling aspects to his personality, but I don't think we can extrapolate from that to anything close to "Mike Portnoy took control of every aspect of Dream Theater's music." Look at the Chaos In Progress documentary. Mike and John are shown disagreeing about something musically, and at no point does Mike try to impose his will on John.
Second, I absolutely disagree that the albums released when MP was considered the band leader are homogeneous. ToT is a little bit, but that was an intentional direction that seemed to have been agreed upon by the entire band. Beyond that... 8VM has eight songs that do not sound much like each other. SC is a little less diverse, but still has 7 songs that don't really sound like each other. BCSL has a general atmosphere, but the songs are still fairly heterogenous within that atmosphere, though not as much as 8VM and SC. DT12, on the other hand, is, to my hear, exceedingly homogenous. All the songs really blend together to me, in a way that songs from SDOIT-BCSL really don't.
I didn't always think this way. I was never one of those "MP plz brng bak stay wiht Drm Thaetar INdnesa durm god MP forver" people. When I first heard ADTOE, I did think it was safe, but I also thought it had some really, really good stuff. And I figured that maybe the next album would be a return to more experimental form. It really wasn't, in my view. I did like DT12, but it did feel safe yet again to me. Only after spending a few weeks with the album did I realize that there was something missing for me with MP gone.
Everyone who followed my top 50 thread saw that ADTOE and DT12 rank similar for me among DT albums, both in the middle-of-the-road range. ADTOE is my 7th favorite and DT12 is my 8th. These are ahead of four albums: SC, WDADU, FII and SDOIT. I regard FII and WDADU as special cases: FII was made with significant interference from the label and WDADU was their debut. SC and SDOIT, on the other hand, are, in my book, the less successful experiments with unconventional styles of the MP era. But I would rather have another album that is unexpected but falls flat for me like SC than another album like DT12 that is perhaps good but expectedly so. My least favorite DT album, SDOIT (by the way, here's a controversial opinion for y'all buried deep in this post), is a very memorable one in a lot of good ways and some less good ways. But DT12 is far less memorable, and if they make another album in a similar style it'll be even less so.
I've come to expect it at this point. I don't think DT13 will surprise me. I do think it'll probably be a good album, but a very predictable one. And I've come to terms with that, and I'm still excited to see if they make songs that I do end up loving (because I do love some ADTOE and DT12 songs, really, I do; BAI is #1, FFH is #7, TBP is #10, IT is #15). But if this is in fact the case and I'm not surprised when the fall of 2015 rolls around, it'll be true, in my mind, that the golden years of Dream Theater had ended in 2010 with Mike Portnoy's departure.