Honestly, the FPS drop is more linked to your character personal progress (old Adventure Journal stuff) than its inventory.
My Alchemist has shitload of stuff, since I use it as a storage character, and I get no FPS drops at all when I try to refine some items… on the other hand, if I switch on my mains, on which I did every hiddenquests/achievements/etc, attempting an item refine freezes the hell out of my game, in both succeed&fail scenarios, and their inventory are empty clean, they include stuff for daily usage (potions and such) only.
I believe this has been discussed many, many times in the past, the most common theory points to the gameclient failing to communicate properly with the server database if you’re logged on a “heavy” character… this happens while crafting items too, you can see this affecting new characters too if you start “investing” on them… nowadays I can’t attempt a refine on any other character than my alchemist because of this…



