It will no doubt improve as the pads bed in. The disadvantage of rear discs on a light car is that they don't do much so will take a while to bed in. Handbrakes on rear discs are known for being weak which is why some manufacturers incorporate a small drum in the disc for a handbrake. Apparently the VW electric handbrake has a motor in each rear caliper which applies the handbrake, rather than a tunnel mounted solenoid with cables. More to go wrong......
The Aero based cars have rear discs and a second, mechanical pair of calipers on each disk, just for the hand brake. A bit overkill, but very effective, they lock the wheels!
But I rarely apply the hand brake, given that putting an automatic transmission in "P" is a rather more effective brake....
