In $\triangle A B C$, the sides opposite to angles $A$, $B$, $C$ are $a$, $b$, $c$ respectively. Given $b \sin C + c \sin B = 4 a \sin B \sin C$ and $b ^ { 2 } + c ^ { 2 } - a ^ { 2 } = 8$, then the area of $\triangle A B C$ is \_\_\_\_
$\dfrac{2\sqrt{3}}{3}$
In $\triangle A B C$, the sides opposite to angles $A$, $B$, $C$ are $a$, $b$, $c$ respectively. Given $b \sin C + c \sin B = 4 a \sin B \sin C$ and $b ^ { 2 } + c ^ { 2 } - a ^ { 2 } = 8$, then the area of $\triangle A B C$ is \_\_\_\_