You get less performance with DX12 because you do not have enough VRAM. I also had a 3060ti and switching to DX12 I lost a lot fps.
My performance has gotten worse with SU11. SU10 l was limited by GPU now limited by mainthread.
That was my first hunch as well. However looking at the stats panel in Dev Mode, with DX12, GPU mem utilization was hovering below 5Gb.
Resolution is 1080p.
So unless there is a problem with the way values are presented, my GPU RAM is not fully utilized, apparently.
Are your values similar at 1080p? Could it be that your screen resolution is higher than mine?
I was running the 3060ti @3440x1440 on high settings which caused stuttering. That was the default a320 departing from Atlanta KATL. DX12 was only playable on the medium preset. I no longer have the card though so I can’t do any further testing. I honestly don’t know whether to trust the dev mode performance counter.
Try deleting that file and relaunch the game.