Right. Losing 66% makes the personal laser defense (PLD) 66% worse regarding electric-power-to-point-of-damage-ratio efficiency. I am going to break down the different modifiers and how they all come together.
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IE: Without any laser shooting speed boost and at 1.5 laser shots per second, Pre-adjusted 30 base damage per laser shot for 75 kW per second. Post-adjusted 10 base damage per laser shot for 75 kW per second.
Regardless of the base damage, each laser shot consumes 50 kJ of energy, and PLD can shoot ~1.5 shots each second. ~1.5 shots per second * 50 kJ = 75 kW divided by a second (1 Joules = 1 Watt / 1 second).
Increasing the laser shoot speed confers a higher needed energy per second.
IE: With maximum laser shooting speed (going from 1.5 laser shots per second to 4.8 laser shots per second), Pre-adjusted 30 base damage per laser shot for 240 kW per second. Post-adjusted 10 base damage per laser shot for 240 kW per second.
Regardless of the base damage, each laser shot consumes 50 kJ of energy, and PLD can shoot ~4.8 shots each second. ~4.8 shots per second * 50 kJ = 240 kW divided by a second (1 Joules = 1 Watt / 1 second).
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I would have preferred that WUBE Went in the other direction and made the personal laser defense shoot slower (by making it harder to be biter proof by stacking PLDs as the WUBE thought it was too easy to stack more of PLDs) and kept the base damage at 30 and increased time between shooting from 1.5 seconds to 4.5 seconds.
This also makes the energy weapon technologies modifier scale worse by 66%* for personal laser defense.
Good luck getting anyone to accept that they should invest significant more resources into an exponentially expensive, repeatable technology to make up for the difference.
*scale worse by 66%: See next section.
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Now, the losses of power efficiency between post-adjusted and pre-adjusted base damage at maximum laser shooting speed at 6 energy weapon damage level (pre-space) are calculated. Energy weapon damage 6 level gives 230% cumulative modifiers. Both post-adjustment and pre-adjustment are assumed to have 240 kW energy demand.
30 base damage * ( 100% + 230% ) = 99 damage per shot for the 240 kW energy demand.
10 base damage * ( 100% + 230% ) = 33 damage per shot for the 240 kW energy demand.
That is still a straight 66% loss post-adjusted in power efficiency compared to pre-adjusted power efficiency, and I don't need to do any complicated math as 99 divided by 1/3 is 33.
To get post-adjusted PLDs back up to at least "99" effective damage per laser shot, I would need about ~890% increase in laser damage modifier from energy weapon damage technology, which is at 16 energy weapon damage for ~103 damage from base 10, and needs 512 thousand of all science packs (not counting from 7 to 15 science pack costs) to match a pre-adjusted PLD at a pre-space-pack technology level. To put that in full context, the pre-adjusted '99' damage from 30 base damage at energy weapon damage at 6 levels only costs 600 of the following science packs: automation/red, logistic/green, military/black, chemical/blue, and production/yellow—no space science packs required.
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The PLD adjusted base damage and increased HP buff and laser damage resistance to worms (the worst part of clearing dense hostile fauna in late-game); I might as well increase the number of spidertrons in my squad by at least 2 or 3 factors. Nothing changed regarding clearing strategies except having more equipment grid, by adding more spidertron to the fauna-clearing group, to play with.
Even with a modest increase to the spidertron's equipment grid and higher quality (damage? laser shooting speed?) to personal laser defense, I don't think there are enough boosts to match or exceed the adjusted PLDs' base damage. See the end of my post with an example of my spidertron clearing build.
Grinding for Q5 across the board is a quick way to make players wait longer before clearing out hostile fauna and have to make more investments (technologies and production lines for Q5 equipment/Q5 Spidertron/etc.). I don't find the idea of making Q5-everything an obligation fun, and at the same time, it is necessary to obtain more resources for factory growth by clearing out the local fauna on the respective worlds.
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That is 23 personal laser defense modules in total, which consumes 1,725 kW or 1.7 MW without laser shooting speed unlocks.
23 * 240 kW (max laser shooting speed) = 5,520 kW/5.5 MW.
The new 'Space Age Fusion Reactor' can provide about 6.25 MW at Q5. I can only begin to guess the new optimized loadout without knowing how big the new Space Age Fusion equipment is.
I can tell you right away that there aren't enough personal laser defense modules in that example you gave to out-demand the new 'Space Age Fusion Reactor's' power yield.
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My typical late-game clearing spidertrons, usually in a group and using the same loadout each, typically have three personal laser defenses, one walking extension, one legacy fusion reactor, and the rest are filled with Shield Mk 2 modules (six * 150 shield HP = 900 shield HP).
I would need nine personal laser defenses (at the same energy weapon damage and laser shooting speed investment after the personal laser defense nerf) to match the current PLD level of damage yield and lose out on no less than four Shield Mk II modules (going from shield 900 HP down to 300 HP) and removed the walking extension. The lowered shield HP makes it easier for the spidertron to die from range hostile damage.
The walking extension is there to help dodge incoming damage from spitters and worms (especially the more dangerous ones). While I can still dodge the behemoth projectile without the walking extension, it will be a trickier proposition.
To maintain the same efficiency level of killing, walking speed, and shield HP with the new adjusted PLD damage. I would need nine PLDs, six shield Mk 2, a walking extension, and one of either Q2 or Q3 of the 'Space Age Fusion Reactor' (9 PLD * 240 kW = 2.16 MW).
That is approximately 84 (16* new space age fusion reactor + 8 walking extension + ( 9 * 4 ) = 36 for PLDs + (6 * 4 ) = 24 for Shield Mk 2s) equipment slots in total, and the current Spidertron only has room for 60 slots. I assume an extra increase in Q# is another 10 rows of equipment room. That means I need a Q4 Spidertron, which is an expensive investment given the grind involved.
*Assuming no change in grid size going from legacy to 'Space Age Fusion Reactor.'
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The proposed balance changes only further highlight the downside of the PLD damage nerf, as it will most certainly negatively impact anyone who opts out of quality mechanics while owning Space Age or doesn't.
I hope WUBE developers are smart enough to realize this is an untenable situation for those who didn't buy Space Age or chose not to opt in the 'quality mod' while owning Space Age and limit the PLD balance change to only those who both buy Space Age and opt to quality mod.
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To be clear, I understand WUBE's need to nerf the PLD.
I think a straight damage reduction put forward in this blog is heavy-handed, especially when you look at the complete picture of all changes that impact PLD put together (spawner base HP, worms increased HP, worm laser resistance damage, lower base damage for PLDs, etc.). I might as well automate the replacement, set up patrol routes for new spidertrons, and walk away while letting Factorio run in the background to do something else for a few days before returning to grow the factory.
A combination of higher energy demand, a slower rate of shooting, and a less severe reduction to base damage (the exact numbers/modifiers/damage-resistance/HP/etc. can be tweaked as more time goes on) would be a better-balanced approach.