I found they are quite tip dependant. After rolling my collection I settled on Xelastic and then dropped down a half size. Felt they were pretty good and best of the bunch. Dots just didn't nail it for me. I then went and got 2 versions of short tips from epro, TW01 and EP01, I've now had TW01 on for a few weeks and really like them.
I've finally figured out that I quite like a stereotypical 'W' shaped IEM. Maybe not strictly linear but the slightly more forward mid suits preference and musical tastes quite well.
Stage on these I completely agree with you. Certainly not the widest but what they do in between is nothing short of exemplary. I actually find too wide a stage ends up being too spread out for me and distracts from the 'music'. You end up switching focus between different aspects or the music rather than enjoying it as a whole. The imaging on Indigo let's you zone in on something specific if needed but the stage is kept reasonable so full experience can be had as well, if you get me drift.
Not sure if yours are a new set or used but the EST's need a bit of time to settle in. Could be brain burn in but I found they mellowed out after a decent run in.
As for BCD, with the right fit it works very well. I'm sat here with my morning coffee listening to The Wall (Reissue, red writing on cover, 24/96) and BCD is in full effect. I've actually got to credit Indigo for giving me a greater appreciation of this album, it never featured much on my Floyd go to albums but it sounds bloody amazing with indigo. The texture on Mother is particularly excellent. In fact, if I had to sum up indigo in 2 words, it would be texture and imaging.
BCD I notice most on deep male vocals, percussion and guitar, electric and acoustic depending on how the guitar set up and quality of engineering.
I also think Indigo can be up there at the boarder line for what some might call harsh, they're quite resolving / detailed up top (my 1st EST iem) and even with MAX I can change a few settings on the DAP and overdrive the treble to the other side of the line. They're nowhere near the resolution of Ra for example (not many are!), but they do have that detailed crispness to them instead of a soft ethereal treble. I find this gives a lot more realistic presentation of cymbals.
Synergy if probably quite important with Indigo (unlike u12t I had which would probably pair with anything quite happily). Don't think you should have an issue with n6ii though. I had N6ii with A01/T01/E01 (way before I had indigo) and would probably put T01 in last place if I was choosing one of those 3 to pair with them. Switch to an ESS from 2 years ago and maybe you'd have synergy issues.
Anyway, give them a bit of time, took a bit of playing about to get maximum smiles from them.