Hydraulic handbrake with stock rear brakes

[Dino86]

Hi,

I installed a hydraulic handbrake (0.625").
I'm using stock rear brakes.

I know in general, the OE rear brakes s*ck.
But even with my hydraulic handbrake it's hard to get the rear wheels locked.
It works on lower friction asphalt. On high friction I can just lock the inner (unloaded) wheel while cornering.
Bleeding is OK, since brake pedal feeling is same as before.

Is it normal that even with hydro handbrake the rear is difficult to lock? In other words, are the brakes even worse than I thought?