Part of the issue is that when athletes are competing at lower levels they may be able to suceed on talent alone. At the upper echelons of any sport though everyone has talent. Everyone is in that 99.9th percentile of whatever characteristics it takes to succeed at the elite level in a given sport or activitity. At this point the determining factors can be training, lifestyle issues (nutrition, sleep habits, therapy, etc) and / or PEDs. At the highest levels I really think we are splitting hairs with the 'talented vs. not-talented' argument. With a few exceptions (and Marion could very well be one) I think that the talent differential at the elite level is minimal. So to separate yourself from the rest of those genetic marvels on a CONSISTENT basis you need to maximize everything you can in training and lifestyle issues. What I think PEDs do is give you a buffer….you can train less than adequately, you can eat at BK every day, you can skip your weekly therapy session, etc….and STILL suceed. It doesn't mean you can't do it without them, it just gives you a lot of leeway from perfection. If you have someone who using PEDs AND training and living well then you have someone who will be very very very difficult to beat.
11.15 fifteen years ago is certainly impressive and certainly shows she has amazing talent. Let's not forget however that running a full half second faster than that is a big jump. Let's also not forget to that be consistently running 0.2 faster than that after having AGED 15 years is also no small feat.
EPO can help a sprinter in several ways….most important of which is probably recovery from hard training. In fact, most if not all of the BALCO athletes were on EPO and a list of other drugs so long you could turn it in to a book.