Comparing rocky planets, density doesn't really matter at all. The range of possible densities for rocky planets is tightly constrained. What matters is the fact that surface gravity scales sub-linearly with regards to a planets mass.
M = 4/3*pi*r^3*d
r = (4/3*pi*d/M)^(-1/3)
a = GM/r^2
a = GM(4/3*pi*d/M)^(2/3)
a = G(4/3*pi*d)^(2/3) * M^(1/3)
We know that it's not (primarily) rocky though because the radius is 2.6 that of earth, but the mass is only 8 times. So it's about about 46% as dense as earth.