While there is undoubtedly plenty of PED use in rugby, I think it's stretching it to say that this was what caused the likes of England and Scotland to beat Argentina and Romania. Romania don't have a league or any of the resources, PED or otherwise, to compete with established rugby nations, while Argentina have plenty of teams in the major European leagues who probably do have access to those things but not the strength in depth, plus you have the problem of not playing as many internationals therefore less experience playing as a unit. Many of the Romanian players simply don't have the experience of playing against top sides week in week out.
It's like saying that it was clearly PED abuse that allowed Germany to beat Australia at the 2010 football world cup. Now, there is probably a stronger chance that the German team had access to top PEDs than the Aussies, for sure, but the quality of the Bundesliga compared to the Aussie domestic leagues and the quality of coaching through normal, non-drug-related means is always going to be superior since there's more competition since football is a completely ingrained sport in Germany and the #1 sport, whereas it faces stiff competition from other sports in Australia and is not the top priority of the nation's sport fanatics or officialdom.
It's like saying that it was clearly PED abuse that allowed Germany to beat Australia at the 2010 football world cup. Now, there is probably a stronger chance that the German team had access to top PEDs than the Aussies, for sure, but the quality of the Bundesliga compared to the Aussie domestic leagues and the quality of coaching through normal, non-drug-related means is always going to be superior since there's more competition since football is a completely ingrained sport in Germany and the #1 sport, whereas it faces stiff competition from other sports in Australia and is not the top priority of the nation's sport fanatics or officialdom.