Well, it's always been thus.
In HG and derivatives. Yet that was criticised above for not being story-compliant.
And spinal one-shot kills invalidates battleships.
T5 is different, as a spinal just punches a big hole through the target, doesn't kill it outright, at least in the ACS system.
The size and armor of the Tigress make it very difficult. The armor removes the threat of turret weapons, save the nuclear missile. But the dampers contain that (especially against a fighter). PAs, even the largest spinals, can not crit the Tigress, nor can it reach down and hit the crew. At best they burn off weapons and leak fuel.
Missile bays... Enough will strip a Tigress of it's meson spinal quite handily, at least according to HG.
A swarm of 1 kDt missile boats with a bay each, will mission-kill a Tigress quite quickly by degrading the spinal. That's just a few months in the yard, but with transport time, that Tigress is out of the fight for many months.
The only thing that can crit a Tigress is a meson gun, the bay weapons aren't big enough to get through the screens. So, that means lots spinal mesons. And those mesons need to be big enough, and armored enough, to weather the zillion missiles the Tigress is going to be sending out (480 bays).
No, the missiles will just strip a few weapons off one of them, while the rest of the meson sleds will kill the Tigress with crits.
Against a decent meson sled, the Tigress' 430 missile bays will only inflict ~10 weapon hits, degrading the spinal two factors. The Tigress will not survive the first round to make any more attacks...
The natural outcome of High Guard is many small combatants, hence the pilot limitation in TCS to force fewer, larger ships. Size is no defence, hence use, in HG nor any other system with one-shot kills.
MgT2 makes a decent case for battleships, missiles, and fighters by doing away with the one-shot kill mechanic (and some careful balancing).
Fighters can't touch the Tigress until the armor is crit down. One crit, and the Fleet Carriers 300 fighters should be able to make 2-4 weapon hits per round (but they can well be readily attrited by the Tigress missile bays, much less its internal 300 fighters).
Fighters' small batteries can't penetrate and can barely hit even a
barn-door, sorry Tigress. Fighters are not combat-viable at higher TLs, only possibly at very low TLs.
Note: In HG fighters can't hit each other, much less attrit each other.
But with the very limited detection ranges in Traveller, they should work very well as recon and possibly skirmish units.
For TCS fans, a Tigress Batron of 8 Tigress with its complement of Fighters costs a mere 3,154,560MCr.
Could be fun to find the cheapest counter to that.
In TCS that's dead meat, just as most (all?) ships in FS.