Let's define failure...
Failure to me would be if there were 6 different boosters to buy and 3 of them became very popular with the community and the other 3 were ignored. This could "fail" because retailers stuck with the unpopular 3 would be pissed by this stock that does not (turn over). BUT, not every gamer is as passionate as we are to come on the Internet and figure stuff out.
I think the Internet savvy gamer is probably less than 5% of the gaming population (even the hardcore!). So eventually, the less popular mini packs will sell at retailers (and they won't restock them, or will be slower to restock), meanwhile they will restock the faster selling SKUs. This doesn't seem to be failure.
Maybe the new sets will just be too pricey for what they offer... It's hard to say without knowing what their sales numbers are like for the previously completely random sets. They could go a TON of directions. They could do a PHB2 set non-random, they could do a 2009 set, they could go back to completely random and just not have crappy minis (crappy sculpts or completely off scales, which I think they are aware of). Themed, martial, arcane, etc.
WotC really isn't a big financial part of Hasbro, so they can still afford to experiment with the DDM line. Supposedly Edison failed 10,000 times to create a working lightbulb, if he didn't experiment--like WotC is with a new format--then he wouldn't have experienced success.
I agree that it is frustrating to watch, to wait for, especially with a hobby that we deeply care about its success. I am glad for DDM and have discovered the joy of buying complete uncommon sets (some common sets too), and rares on eBay. Oh baby.