Here is the Tea,
A lot of people conflate rarity with power. However I feel like that is saying the “super rare chase” items are Stasis Prison from PoE. An item so rare its not even listed on the market, however the difference is Stasis is complete trash. Where as the chase items in LE tend to be build around or flat out required for pushing corruption.
A good example is the Poison/Bleed Flurry build still uses Bastion, yes even the dual wield mastery uses Bastion. Why? well its powerful sure, you get an entire layer of defense all in one item, but that does not really answer the question does it? Its more about how chase that layer of defense is. Resistances and armor are the easy way to layer some basic defense, everyone can do this. Whats next? Crit Avoidance is the next one and its also pretty easy and cheap to get. Keep going, Dodge is really only obtainable if you have the build in skill support so we have to set that aside for the moment. That leaves block, and given how block works and the required investment to reach the same levels without a bastion you are left with no real good option.
So we have the basic settled, perhaps you could use it as an argument that bastion needs more nerfs and I find this argument eternal. I would rather see more items in general find a use then nerf the top 1%. Moving on, in my view its more about the investment requirement of the defensive layer itself, like I said above, once you get the basics in place you do not have a lot of options to increase your survival leaving you with a paradox of sorts.
Sacrifice your affix slots to get that layer, leaving you overall in a much reduced offensive state. Or push through and play LE like it is a hit less speedrun because you are likely going to get one tapped when pushing higher corruption.
TLDR: Bastion is not a chase item in the standard sense, its just another layer of requirement to meaningfully engage in higher content. More so when your class does not have access to the other esoteric forms of defense like dodge/ward/movement.