Stacking Basics Of Pain & Pressure Point Cluster Jewel?

I noticed in POB that when I stack the following :

15% Increased Critical Chance Medium Cluster
Basics Of Pain
Pressure Point

My DPS gains seemed to increase - but at a decreasing rate … till a state where my DPS actually decreased?

I then noticed on Poe.ninja that those who were using these passives almost never use more than 4.

Am I missing something?

Thanks in advance.

For the max 4 nodes in medium, it's because of efficiency: this way you get 1 point that connects to the parent Jewel socket, 2 Notables and the last node is a Jewel. This way you have 3/4 passives spent in Notables/jewSocket.

For the increase, I don't exactly see why it should decrease, given that both Basics of Pain and Pressure points give some extra DPS even if you somehow get to 100% critChance

Sorry, I meant stacking multiple similar jewel clusters.

So in POB, for eg my DPS is 10M, then after I equip the first cluster, it shoots to 11M.
2nd cluster I equip then becomes only 11.5M. 3rd Cluster becomes 11.7M. 4th Cluster becomes 11.75M

Then suddenly 5th cluster becomes 11.5M? I kept equipping and then replacing it to clarify the figures are actually reading right?

I closed POB restarted it, and same results.