I don't think it qualifies as a permaculture approved technique.
The fact that you have some productive ones and just a few duds would indicate that the duds are in the wrong spot or otherwise compromised. I think I'd cull and try something else in that spot.
To maintain the open sites and to prune
the branches, it has been felt that it was necessary to burn
over lowbush blueberry areas. It is believed that some of
our native lowbush blueberry barrens have been managed
by burning for an estimated 900 years.
A few national forests, such as the Chippewa National
Forest in Minnesota, develop and manage sites as
blueberry picking areas. Periodically, a few hundred
acres of blueberry area are burned in the Chippewa to
encourage new and more productive growth of the native
blueberries. Sites are selected for management based on
the availability of existing plants, the accessibility of the
site, and historical picking use. Late fall burning is
preferred. However, burning has drawbacks. If the
surface gets too hot, burning can destroy the organic
layer of the soil, thereby exposing rhizomes to heat,
drought, and extreme cold.
I don't think that applies to your situation.
Burning Low Bush Blueberries
After the leaves have fallen in the autumn in the time to spread a thin layer of straw across the field. The plants are dormant, foot traffic will not cause injury. Straw is preferred over hay because the stalks are hollow. In Maine, oat straw is widely used. The hollow stalks allows better air flow resulting in a faster burn. The fuel is consumed before the heat can penetrate deeply into the ground. The burn is done in the spring, before the blueberries have begun to bud, but many weeds have come out of winter dormancy. A few dry days in April and one without a strong wind is all you need. Add a flame to the downwind side, the flames will walk across the field. A few men with backpack sprayers will be able to contain a flare up.
The burning of the low bush berries has several reasons. Weeds can quickly grow to smother out the low bush plants. Burning the field every other year knocks down the weeds. The low bush plants are able to recover because the burn is quick and above the soil surface. Low bush blueberries can propagate by rhisomes. As long as the soil is not cooked, the plants will jump right back up. The ash keeps the soil acidic. The potash promotes rhizome growth. There are some pests which overwinter in the dead top growth of the field. The deeper this thatch layer, the greater their chance of survival. The burn destroys their habitat. The method is quick and economical.
Low bush berries do not bear fruit the first season. It will be another year until those juicy berries show up. It is common practice to burn a field every other year. A 2nd crop is a gamble. The plants will produce, but the weed growth can interfere with harvest and pests can get out of control. A 3rd crop is likely to be miserable and in an overgrown field.
In a fast burn, not all the stems will be destroyed. Many will recover, but will not bear fruit that season.
High bush plants can be propagated from cuttings. If the soil is depleted, taking basal growth cuttings and relocating the plants would be a way to keep them going.