After analysing 'non-official' drugs using HPLC, GC-MS, TLC and the like, and seeing what is in these tablets, and comparing them to the official ones, I would never buy online drugs.
Many are packaged in legitimate packaging but are non-legit formulations with levels of impurities in which are either dangerous and/or take away from the assay of the main drug.
If they are legitimate, it is quite likely that they have been stored improperly, or are a batch gone wrong that has been knocked-off or even poisoned.
We used to get called in on a Sunday morning sometimes, so customs/police could charge someone once they had arrested someone.