Using your example of swarms>turrets>phantoms>swarm
You have the Phantom as an archetype, you can't tell me all swarm ships are the same. The tie fighter is better than the z95 for it. An outer rim smuggler or blaster turret hawk isn't the same as Han or chiraneu. There are definitely tiers. So ships and combos are better than others.
True, the Tie Fighter is imo a far superior swarm ship (Better dial, far better action bar) but does that make the Z-95 low tier? **** no. It's a solid little bastard of a ship and a very potent mini-swarm
So, is it the ship that's lower tier or the build that's lower tier?
the distinction matters quite a bit
Now true, there will always be superior ships in a straight one to one comparison just as there will be head slappingly stupid builds (naked rebel operatives), but taken as a whole many Squadrons seem surprisingly even in strength, As ships fluctuate depending on how they interact with one another, both allies and enemies, attempts to fix them to set "tiers" become more and more difficult.