I'm not sure I'd call it a losing battle. But, I agree vigilance is necessary.
But, I also view anti-doping measures as more of a safety issue than a fairness issue (maybe 60/40-ish). First priority - prevent athletes (and their coaches/sponsors) killing or crippling themselves with chemicals. Second order - guarantee some baseline level of fairness (because without it, the fans go elsewhere).
This isn't really different than rules in motor racing. Gotta keep the drivers safe first, and keep the race entertaining (nobody outside Italy wants to see two Ferraris dominate every F1 GP).