I have this too..I thought it was fixed in the latest patch but it was a placebo and "wanting" it to be fixed..
I think the dev's possibly don't know how to fix this..
It is truly maddening and I refuse to play it or any future games if this engine is the platform if this can't be fixed...
The support is okay with Larian as far as comm, but I think they are somehow trading off Quicksaves as an alternative fix to the unfixable mem leaks...hope I'm wrong
Things to improve a little on Med textures, less herky jerky but still slows down over time...
On a 680 SLI setup, this should NOT be happening