I think the outside influence on FII itself, where it resulted in tangible changes are obvious -- the changes to Burning My Soul (Hell's Kitchen), Take Away My Pain, You or Me, the demos show the changes, and that is pretty direct in regard to John sitting down with other people to make changes to the tunes.
What's harder to really grasp is how basic conversations between the band, and other people influenced how those songs shaped up in the tone and feel. It's hard for me to describe with words what I mean here, but essentially it comes down to the non-tangible of would John or whoever else wrote or played a certain part a certain way had the outside influences never talked to them to begin with? It's really hard to tell.
I actually think Falling into Infinity has some of the more passionate and emotional performances on it from John that I've ever heard (or heard since).
I'm of the opinion DT has always needed a producer they trusted to make suggestions to change things anyway...when left to their own devices, DT tends to take the long way...the really long way to get to a point. Whereas a nip and a tuck here and there to bring a song from 15 minutes to 11 minutes can make all the difference (case in point -- the solo sections of Endless Sacrifice -- way too much) between turning a good song into a great one, or a great one into filler because of length.
But DT's fans are a mixed bag, so obviously, for the majority, what DT does on their own is preferred. I'm just not with that group. FII, to my ear, was a step in the right direction. I didn't believe in co-writes with outside people, but I very much liked the fact that suggestions of others outside of the band were being incorporated to make the record a more listenable and accessible album. I don;t think art was sacrificed for accessibility (which is where I'd draw the line). I think it was a good balance. But most disagree, so...