Improved Uncanny Dodge

While Obsidian has not confirmed the existence of improved uncanny dodge in NWN2, it is a class feature of both the barbarian and rogue class which have been confirmed.

3.5 Uncanny dodge
A character with this feature can no longer be flanked.

This defense denies another character the option to sneak attack the character by flanking her, unless the attacker has at least four more class levels, in their class which provides sneak attack, than the target does.

If a character has more than one class that provides improved uncanny dodge (or uncanny dodge) the total levels of both classes are used to determine the minimum class level required to flank the character.