Okay, EPO will give a placebo effect. All drugs give a placebo effect, real drugs or sugar drugs. There is a study showing the effects of administrating placebos in different forms, small pill, big pill, needle etc. A small placebo pill will give the smallest placebo effect. The bigger the pill the bigger the effect. A needle gives the highest effect. Placebos still even work after the doctor telling the patient it's a placebo. I will find the study and post it ASAP.
Your question on longer than 5k efforts. You are missing the point. EPO increases your aerobic capacity. The longer the distance, the more you rely on your aerobic system. The marathon is a purely aerobic race(i.e your heart and lungs do all of the work). Your marathon pace is your aerobic threshold.
By improving your aerobic threshold with EPO, you also improve you're anaerobic threshold thus making you faster at shorter distances as well as longer distances. You think EPO only affects Vo2 max which is false, it is a primarily aerobic enhancer but the effects push all your thresholds higher. This is why endurance athletes have a base phase, it's to build your aerobic engine. The bigger your aerobic engine is, the faster and farther you can go.
On HGH, steroids etc. HGH is just as important as EPO. The recovery effects of it are incredible. I have mentioned this numerous times but here I go again. When I was doping, after a month of first taking HGH, the complexion of my skin was nothing short of perfection and I could read the smallest of print without contacts for the first time. HGH is highly respected in endurance sports.