I checked, had three accounts on DX9 and two accounts (the new ones, which are RAF linked to existing accounts) defaulted to DX11.
They're all set to DX9 now.

Pretty sure 10x DX9 is going to work better on a single card, then 10x DX 11.
Also will lower the settings somewhat; only seeing objects/mobs/creatures further away is a priority, beyond that just high enough to notice things like Ring of Frosts on the ground...