Bought my RE0 about two months ago when my ADDIEMs died. Thoughts:
Comfort: These are very uncomfortable. I haven't found any of the tips to be amazing, but I've settled for the ones with the best seal. The bi-flanges are soft and hard to get in properly. With the single tips the ridges on the IEM body rub my ear at times with doesn't feel too good.
Sound: They sound cold. Very precise and accurate, but they are too cold for my liking. I feel like I'm dissecting songs rather than listening with these. The mids and highs are fantastic, but the lows are worse than the AD700s, which I'm shocked.
I like these, they've grown on me throughout the 100 or so hours of use, but I prefer my ADDIEMs personally.
I agree with your observations. The lack of bass is because it's just so difficult to get a good seal with this IEM no matter what tips you use. The best seal I get is with the Comply tips but they just murder the SQ. You can try bumping up the lower frequencies with the EQ but of course there's always a downside to that