Fighting Cutters, where they don't have support from faster vessels, is boring:
Source: https://www.youtube.com/watch?v=1KYm62iVxQE
Source: https://www.youtube.com/watch?v=x13SGjUjAoY
That is how the majority of my CMDR's encounters with hostile Cutters go. It doesn't really matter what medium I'm in or what it was built for; eventually I'll knock out all the SLFs and work through all the SCBs (much faster if I have feedback rails, of course, but I often don't) and the Cutter will either leave rather than risk destruction, leave when it's ammo runs out and it can't open up enough distance to synthesize, or explode if the pilot just doesn't care.
The Cutter is the most expensive ship in the game, and it requires a rank unlock just to get it. It's also a lot more intensive to fully engineer.
I guess I'm a bit confused why your Chieftain, one of the cheapest easily-accessed medium combat ship in the game, should be able to defeat such a thing.
You're attacking the battleship Bismark in a dingy while complaining about it's "ridiculous" defenses. I think what's ridiculous is your approach to PVP.
The Cutter isn't a battleship and the only thing it has going for it in combat is it's enormous shield pool and relatively high straightline speed for it's size. If it doesn't have wing support, it generally has to rely heavily on SLFs or turrets to fend off anything faster than itself.
Nine times out of ten, the Cutter is destined to lose (be forced to retreat) against any competently flown medium...it's just going to drag on forever. That's the issue here. It's not that Cutters are hard to defeat, it's that they are tedious to defeat. The outcome might be set in stone before the fight is even joined, but you'll need to endure twenty minutes of RSI inducing 'gameplay' to reach it.
Shields are a virtually perfect, universal, defense. There are no weak spots to target, no room for fancy tactics to stage a reversal...it's pure attrition. You either get lucky with enough torpedoes to knock out the generator, or you grind though the long way.
How do you make hull tanking viable, without it being completely overpowered and just a new OP "meta"? No pip juggling, less power plant needed etc etc. It has so many advantages, they just HAD to nerf it obviously.
It
wasn't overpowered before. It was just barely competitive.
Source: https://www.youtube.com/watch?v=Qq9TDEvg-tU
Stealth mechanisms are what made it competitive, and the depreciation of those mechanisms, along with shield inflation dramatically outpacing hull/module inflation is what rendered it non-competitive.
In the current state of the game, weapons cannot be effectively employed while silent, and emissive is an absolute hard counter to any attempt at reducing sensor signature. A shieldless ship cannot readily break seeker lock or subsystem targeting and has a vastly lower total 'health' pool than a shielded setup. Unless a ship has stacked anti-missile defenses to the exclusion of others, seekers will rapidly strip away weapons, or knock out thrusters. Long range hitscan weapons, especially rail guns, and especially in conjunction with emissive and super penetrator, allow modules to be reliably sniped at extreme ranges where no evasion is possible.
Hull-focused and hybrid combat is much more dynamic and entertaining than combat between setups reliant on shielding. There are more options, both offensively and defensively, and more meaningful tactical considerations than when it's just shields. With a shield focused setup, there are too many certainties...as long as the shields hold, you don't have to worry about anything else, but when shields are down a few lucky or well-placed shots can turn the tide of a fight without things degenerating into raw damage in vs. damage out. Scenarios whose outcomes are reliant on more than just whose health bar is going down faster are vastly more engaging, IMO.