Sorry dude when you said to have a opinion i figured you were refering to the issue in regards to the OP's theory. And in that regard i think it is naive to think that phasers can be
easily adjusted to every possible setting available to them when they have clearly shown a big range of abilities and effects.
BORGHe even mentions when they first meet The Borg in Q-who although he disregards it rather poorly with a comment about it not being a tactical cube although we know for a fact that normal cubes are the main borg vessels and powerful enough to be used individually for assimilation of some times entire cultures who obviously must have fleets of combat ships.
So to dismiss their construction as
"a wispy conjunction of vertical and horizontal pipes and support beams" is absurd. We clearly see 3
single shots from the D's phasers put 3 dirty great craters in the side of the borg cube, the sides were over 3 square kilometers so the craters were from 500-800 meters in diameter.
One hit was near the edge of the cube and we clearly see a lot of the phaser energy is lost as the edge is destroyed and the rest of beam heads off into space, however it does reveal that the cube is far from being even close to
"a wispy conjunction of vertical and horizontal pipes and support beams" and is in fact has a lot of internal structure and mass that needed to be disintigrated.
I would say a conservative estimate of the crater by the edge is at least 500m in diameter and at least 200m deep at its deepest point (very conservative estimate) although it is on a corner, mass-space il guess at 50/50 so i do not offend either side.
Do not ask me to do the math im a moron.
The 2 other craters that were caused by individual shots are more towards the center of the cube and obviously took all the phaser power, as such we cannot come close to seeing just how deep the craters are into the cube or how much phaser damage was done internally but we know the 3 shots (well 2 and a slice off the side) caused damage to "20% of the enemy vessel".
We know that the cube measured 28 cubic kilometers in volume, so it depends on how you think worf did his calculations regarding his damage report and how much the cubes deep internal structure-empty space ratio was in regards to calculating the mass disintigrated by those 3 shots.
DRILLINGThe crater effect shown against the borg clearly shows that unmodified phasers at high power are not particularly fussy about what they disintigrate and in what pattern.
He clearly points out that the drilling took around 48 seconds after hours of modifications.
So we know:
1. That phasers disintigrate matter at even a reasonably low-medium power settings effectivly let alone on a high power setting when it can disregard neatness and just wants to disintigrate large areas of matter.
2. That time was obviously not a issue as the OP clearly points out they
"took hours to modify the Phasers for this job".
As such we can say that 1 + 2 =
plenty of time and effectivness at low-medium let alone high phaser power to dig a dirty great crater to the 1600meter depth required let alone a narrow hole.
They were obviously using the time to modify the beam so it drilled a nice neat hole instead of just blasting a crater, it also reasonable to say that they would not want excess phaser power to disrupt, dislodge or even weaken and crack lumps of the tunnel wall for when ppl were in the hole.