The potential benefits of doping are so obvious it's hard to believe they wouldn't be doing it. Swimmers certainly embraced the faster swimwear during the period when it was allowed.
I posted something on Torres last year. I compared her comeback with that of Janet Evans, who is actually a little younger than Torres, and who as a distance swimmer might be thought to decline in performance a little more slowly than a sprinter like Torres. Evans failed to make the Olympic team, and her performance seemed quite a bit more realistic than Torres. IIRC, she was unable to match her best time when she was in her twenties, which is what you would expect. Same with Mark Spitz, more of a sprinter, when he tried to come back in his forties. Granted, Evans and Spitz were coming back from a much longer layoff than Torres was, but I really don't think all of an age-related decline can be avoided simply by staying active most of the time.
There's a two-fold problem. First, you can't perform as well at forty as you did at twenty. Second, even if you could, the best times twenty years ago are not world class today. Some of that is no doubt due to doping, but not all, because swimming times have been plummeting dramatically for decades, long before EPO, and probably before steroid use became widespread.
I think the racism angle is overblown. The Chinese girl's performance was much harder to explain than anyone else's. Remember, she actually had a final fifty split about the same as Ryan Lochte's. In contrast, Chinese swimmer Sun Yang dominated the male distance events, and no one pointed a finger at him. Certain Korean swimmers, and before them the Japanese, have emerged rather suddenly onto the world scene, and no one accuses them of doping.