Cross-posting this here since a majority of players don't look at the PTS subforum.
Meticulous Disassembly seems to work as follows, now that it's finally "fixed" on the PTS.
When you are at 0/3, 1/3 or 2/3 in your deconstruction/refining passive, it adds 1 level to the passive (so 1/3 becomes 2/3)
When at 3/3 in the passive + Meticulous Disassembly star slotted = Old drop rates + approximately 12.5% (best guess as of right now) for improvement materials gotten from refining.
Data and test results in the Google Sheet below.
https://docs.google.com/spreadsheets/d/153tkynjLNvEY85RbQq2X1DAFeuE2MPL2iTTdjpdnuiY
Tenacious Dreamer - Hurricane Herald - Godslayer - Dawnbringer - Gryphon Heart - Tick Tock Tormenter - Immortal Redeemer - Dro-m'Athra Destroyer
The Unchained - Oathsworn - Bedlam's Disciple - Temporal Tempest - Curator's Champion - Fist of Tava - Invader's Bane - Land, Air, and Sea Supremacy - Zero Regrets - Battlespire's Best - Bastion Breaker - Ardent Bibliophile - Subterranean Smasher - Bane of Thorns - True Genius - In Defiance of Death - No Rest for the Wicked - Nature's Wrath - Undying Endurance - Relentless Raider - Depths Defier - Apex Predator - Pure Lunacy - Mountain God - Leave No Bone Unbroken - CoS/RoM/BF/FH Challenger
65,385 achievement points