In several cases yes, but in a lot of others no. It all depends on what you expect from your CR. If you wanna get high up in arena them I'm sure any of the Gladiator Suites (never tried them as I don't pvp) or any other specialised pvp CR will outperform Singular, if you wanna do anything else however then Singular or the free Tuanha is probably a better bet. Xcesius' YRB2 does a really good job for raiding as an all in one, so does Oracle2 for healing specs and they only cost about the same as some single spec CRs.
This is also where quality control comes in, are they offering anything more then Singular does and should those CRs even be on the store?
Now I'm far from an expert when it comes to ffxiv and I don't even have a level 50 DoW/DoM class yet so this is definitly a question and not a statement. Don't all in ones make more sense with the multiclass and cross-class skills? Maybe split in AiO DoW and AiO DoM CR?