Far Cry 3 is without doubt a more GPU-intensive game than Divinity.
Not necessarily. GPU intensity isn't directly connected to visual fidelity, as visual fidelity is subjective and doesn't correlate with what is being rendered or calculated in game.
The only thing you can do is update drivers and the usual, the game itself doesn't have any performance issues. Having high requirements to run well doesn't fall under a 'performance issue'.
