If a big anchor can't compensate for poor anchoring technique, neither can luck. But either or both can work most of the time.And as others have said, a big anchor does not adequately substitute for poor anchoring technique. I certainly never gun my 50HP in reverse to set the anchor...maybe 2000-2500 RPM max which probably isn't much more than 10HP. I usually only back it down until the boat stops moving and a few seconds after that
Based on on your description of your technique, you've been lucky indeed.
On Conch Cruisers' trips to FL, the Keys and the Bahamas over the past three years, I have observed boat after boat after boat drag anchor. I don't believe there is one member of the CCs who has never drug anchor at least once, and that includes yours truly. Some have drug multiple times, a few at nearly every anchorage. The vast majority of CCs have some variation of the lightweight anchor; Danforth, Guardian, West Marine et al. By my recollection, since accurate records don't exist, the vast majority of dragging incidents have involved not failure of a set, but instead falure to reset on a wind shift.
Lightweight anchors are prettty well know for this tendency.
perfectly with 15' chain & 150' rode plus some room to spare. I never had a problem. Extremely happy with it. I usually let out 5 times rode to the depth. I slept on the boat on three different occasions while anchored down and no drift. I was also out during Fleet Week last year on San Francisco Bay, anchored near Alcatraz. Frank, we must have been within an earshot of one another, provided the Blue Angels weren't doing a fly-by. The depth was approx 45' so I let out all my 150' rode with just enough to cleat off. The winds picked up to 15 knts+ in the afternoon. No drift what-so-ever. I probably don't know the difference between a fluke & danforth, etc, but it looks just like Paul's, so must be danforth. Very happy with the hook. 
