WADA has become more proficient at detecting EPO microdosing. Blood transfusions easily trip the ABP (the ABP is very sensitive to transfusions - that was it's main purpose when it was designed back in 2008).
On testosterone, the CIRC test can detect even very small amounts of synthetic testosterone (the test can distinguish between natural occurring cholesterol-based testosterone vs plant-based derived synthetic testosterone). No need to rely on the old-fashioned T/E ration test which sets a limit of 4:1 T/E ratio for a positive. Plus there's the ABP steroid module that'll pick up small amounts of anabolic steroids even the compounds with short glow times.
IMO, I just don't see how biological doping can be used effectively these days unless teams/riders are paying off authorities to look the other way?
The ABP is pretty good in theory, but how well does it work in practice? Kreuziger got out of a sanction, there's plenty of scientific literature criticising it, we've seen the highly suspicious self published blood values of Horner from the 2013 Vuelta remain unsanctioned, Juanjo Cobo as mentionned above...
It only applies to the pros too, so you could try to establish an artificially high baseline on younger athletes by using blood doping before they are enrolled.
Regarding testosterone, afaik the isotope ratio test is not used routinely because it's expensive, it's more of a "smoking gun" when suspicions are high because of a high T/E ratio or of anomalies in the steroid module.