The theory behind duals coil makes sense : V8 engine in a car delivers way more oomph than you run-of-the mill 4 cylinder. It also guzzles way more juice

.
Double set-up also has potential for double trouble. Poor design and shoddy assembly will negate all the performance increases. A well-made and carefully pimped 4 cylinder can easily outperform some haphazarly slopped-together V8 ...
Same with coils. If you get to the 'sweet spot' (i.e. where liquid viscosity, wicking speed, air flow, coil temp and coil surface are balanced) you will get amazing results even from low-end clones. It's for a good reason that many vapers chuck out the factory set and tweak it to their own.
Take something and tinker around with it to improve it. Vaping community has been - and continues to be - exceptionally good at that.
And that feedback drives the manufacturers too.... kinks and bugs encountered by the vapers get ironed out in the follow-on model...
which one hand means that manufacturers often put stuff on the market before its really been tested thoroughly ( Well, nothing new there - any window release needs and average of 3 service packs, 60 updates and 400 bugfixes to become moderately stable

).
One the other hand the manufacturers do listen, which is of course in their best - economical - interest. With forums like these, word spreads fast about the good, the bad, and the ugly ...
And the 'spread' in mass produced items is of course enourmous: I remember me ole ego-t at the beginning, some attys lasted for months, others quit after barely a week...
Could well be that u unlucked out on the 'spread'....