yep your settings are incorrect if your getting lag. i have seen that game on much weaker systems playing smooth as silk so do as suggested and select the best settings for the game rather than just maximum.
the things that cause the biggest performance hits are AA, soft shadows, soft smoke and depth of field. disable or reduce all of em... remember just because your card supports dx11 it doesnt mean it actually has the grunt to run such high end features... on the most part the cards are decent enough to run high textures and x4 fsaa... other settings will vary depending on your system.
have you left the game running for more than a few minuets? i thought my pc would not run it either. then i played through the lag for a few minuets and the game smoothed out!!! getting great fps now. just stick with lag awhile and c if it improves.