The game does not support SLI or Crossfire setups, so it is adviced to turn these off when playing Divinity II - Ego Draconis. The game will run faster if it disabled.
I can confirm this as
false - for me, enabling SLI (using AFR2 with 2 Nvidia 8800GTXs, Forceware 195.62 on a WinXP SP3 setup) improved framerates from 25-30 to 45-50 (2560x1600 resolution, High settings).
The only graphics problem I have seen is lack of anti-aliasing (widely reported and, frankly, rather annoying) and flickering if either of the "Timeslice" options are enabled (which occurs regardless of SLI settings).
I am using the No-DVD patch in case that is of significance (standard procedure for any games requiring media checks, to avoid long-term wear on discs).
Video memory usage is unusually high though (700MB at game start) so anyone encountering sudden slowdowns (framerates typically drop to single figures if usage exceeds the videocard VRAM) may wish to check their VRAM usage using a utility like
Rivatuner. Lowering texture quality or resolution should reduce VRAM usage. SLI/Crossfire can't help on this issue.