This is one of the more interesting threads around here, as it goes down many rabbit trails!
I don't mean that in a bad way, if I did I'd be as guilty as anyone or more.
To each his own, but I'll agree that the multi-mode isn't the Rev2s biggest strength, which doesn't bother me though, and don't think it's intended to be. Neither do I use both layers that often anyway, I find using 2-3 OSCs more than enough in most cases. And I only have the 8-voice version, so I'd really be compromising long release times otherwise. I actually haven't found a big enough reason to upgrade to 16 yet. Which is also great about the Rev2, for those on a budget, and still having the possibility of upgrading later on. But I think it's great that the multi-mode possibility is there, should the need arrive, and making for more ways for different folks to use it whichever way they want.
I, too, like to have as much as I can plugged in and played live simultaneously, thus being able to tweak sounds on each synth as a piece evolves, not having to go back and record that part all over if I find I'd like to change something just a tad. Keeping as many possibilities open as possible. Multi-mode isn't always that bad or compromising, sometimes to the contrary, it depends on the synth, but I suppose it's mainly digital ones and samplers that have a better implementation of it. Not all have shared global effects, and many have a lot of extra outputs, for routing through external effects as well. I have a Roland JV-2080 and an ASR-10R, both being somewhat versatile in this area. It saves a lot of space, which I don't have a lot of, and even though I don't use the extra outputs that often (the same being true for the Rev2), I love not being restricted to one pair of outputs or one patch per synth, should I need it at some point.
Sure, in a way I'd love to own lots of other synths too, but then again I really don't see the need to, even if I had the space. I've let a few good ones go not because of limited space or budget, but because they can only do so much, and I find it hard to justify keeping a synth or musical equipment just for that "one" sound or area at which they excel. I find myself wanting less and less rather than more actually, as I think I'm/we're in a way spoiled and/or distracted by too many possibilities and too much equipment. Limitations often fuel creativity, while at the same time I want each piece of equipment being as versatile and capable as possible. I think of it as being "economic" in ways other than monetarily. That's where the Rev2 comes in, for me, and then getting the most bang for the buck at the same time doesn't hurt. I know it cannot exactly "replicate" the character of some other synths, but it can probably get close enough for me in most cases, imo. I understand why some would want a P6 and an OB6 to compliment the Rev2, but personally I couldn't justify getting either. The Rev2 has so much more potential in sound design, that I don't see the point. I'm not saying those who do are splitting hairs, but if I were to get one I'd sure feel like I was doing just that. It might not be as "immediate" as those, but for those of us who actually LIKE programming sounds, well...
Though I, at times, have been on the fence about parting ways with the Rev2, I probably never will. I just don't see anything around that could replace it atm, as I'd prefer to have just ONE analog poly-synth.