I am sick of "RE0 lacks bass". The following is not a snobistic show off, but rather attempt to analyze this annoying issue.
RE0 is very refined and well balanced. It is quite common that such sound sig is not appreciated by noobs. Many of them ask for more bass, since it takes time to educate yourself to headphone/earphone type of bass, which is missing tactile feedback.
RE0 sound can be improved overall and bass weight can be increased in particular. It benefits from good seal, which requires some efforts to buy extra tips (stock are not good) and select the right one. Quality amping (not E5) is also appreciated. All these tricks are not popular with noobs.
So, why there are so many noobs unsatisfied with RE0? I beleive that this is a matter of new $79 pricing. It makes RE0 affordable to many junior head-fiers (not in terms of post counter) but does not make them to value their purchase. There was no huge criticism of RE0 bass before when it was priced at $200 (or simillar, can not recall exactly).
Those who consider RE0 lacks bass, should try ER-6i or even ER-6. They are also very affordable, so why not?