Please note that while it is perfectly true that battleships are better able to face missiles and small craft, the text talks about vulnerability to the damage faced while standing in the line of battle, that is to say, the damage dealt out by spinal guns.
All this would be fine if only the other side didn't have meson spinals. However, they do. And they have had merson spinals ever since the Terrans invented them 3000 years ago.

The flaw of discussing ships in isolation rears its ugly head again.
The Admiral that starts with his Meson Guns in the line of battle loses. Period.
A HG BB, contrary to popular belief is better off without a Spinal Mount. The only reason for having one is because you can and it pads out the USP. Consider for a moment what happens to the biggest ship in the opposing line, it gets targeted by everything with a remote chance of scrubbing weapons. The first weapon hit knocks points off the Spinal Mount, every 7th after that reduces it further. They accumulate fast when the entire enemy line is focused on reducing your big ships.
The Spinal Mount gets only one turn of firing at full effect. That is it. If it gets lucky, great, but the odds are it will not make a difference. What will make a difference are the huge banks of missile bays.
So where are the effective Spinal Mounts? On Cruisers. They cannot sit in the line of battle until close to the end when the volume of fire has been much reduced, ideally close to 0 giving the Cruisers, whom also have the legs to chase stuff, the opportunity to deal out damage over multiple turns with Meson Guns that only get scrubbed slowly.
So yes, I would put the Tigress in the line of battle (after Fighters and Escorts had already had multiple rounds to soften them up and reduce any Spinals presented), but not because I think the Meson will achieve anything, its the missile batteries that will achieve the most effective results.
Unless you're going to tell me that a Factor S meson gun is far less dangerous than a Factor T (instead of being almost as dangerous; only one critical hit less), that is not a convincing argument.
Funny you should ask, that is
exactly what I am saying.
Effective tactics aside, the Imperium at TL15 is qualitatively miles ahead of a TL14 opponent. As already noted, Spinals only get one turn of firing at full strength. But, lets assume for a moment we are talking that single turn of firing and both sides are mug enough to present Spinals first.
TL15 T Meson hits on 4+ (+1 for computer, -6 Agility, +2 size, +0 long range) = 7+ to hit, it penetrates TL14 Meson screen on a 3+ (+1 for computer) = 2+, so automatically and most hull types automatically. 7+ (21/36) makes ...
58% chance of a hit.
TL14 S Meson in return hits on 4+ (-1 for computer, -6 Agility, +2 size, +0 long range) = 9+ to hit, it penetrates TL15 Meson screen on 5+ (-1 for computer) so 6+ and lets call it automatically on hull type although needle types need a 4+ to penetrate. 9+ (10/36) followed by a 6+ (26/36) makes ...
20% chance of a hit.
You need more than 2.5 TL14 Spinals to get the same hit odds. So yes,
TL14 S-Mesons are a lot less effective than TL15 T-Mesons.
And that is before you consider the rate the TL14 Spinal will get reduced by TL15 missile bays. Meaning that if you do not think this through, in combat you find your Spinals are reduced to be insignificant after one round.
Sadly most then assume the game is broken rather than consider they used the tools available poorly. A scalpel does not make a good hammer, little wonder that it disappoints when it gets used as one.
All food for thought.