Crisis fragment drop suggestions; Set order, Atlas generation adjust or singular-key type.

I'm on a hunt for a set of Arbiter fragments and have been hit by a string of bad luck, finding 4 iron citadels, 2 copper and 0 stone.

Exploring the atlas and seeing, again, a citadel you don't need is a painful and demoralizing experience, especially in the off-chance I see another player find one of each in their first few citadels.

1. Uniform order drop
Retaining most of the current system, if possible to have each citadel boss cycle through a checklist of already dropped fragments.
At the least, preventing the boss from dropping the same fragment as last time
At most, ensuring the next fragment is the next on that checklist.

1. Atlas generation
With the same aims of the previous, this would also guarantee a set order of fragments, natural to the endgame cycle by ensuring the next citadel you find is also on the same checklist type idea of suggestion 1, a set order. I assume also this is far more work than it appears and may be impossible to integrate with players' already existing Atlas layouts.

3. Singular key type.
The suggestion I like the least, would be that the arbiter fight still requires 3 fragments, but the fragments themselves would be reduced to only one variation that can be dropped by any Citadel boss.

I understand enhancing the rate at which players encounter Arbiter wouldn't arrive without some economic consequences and would assume that when needed, the drop chance of these fragments should be reduced if any of my suggestions are truly considered.

I am more than happy to enter a citadel and get nothing, knowing I'll have the chance to get one at any citadel next time, rather than explore the map dreading the next citadel spire I see is the wrong colour.