get new struts, and new tyres that will help, other than that just grin and bear it, put more air in the front tyres. Personally the steering on my rona should be heavier, no ps too and more weight over the front wheels. I find it a breeze to turn the wheel even at parking speed. I have driven my sis's ke70 and would say that her steering would be slitghly hevaier than mine, but her tyres rarely have the proper air in them plus it has worn shocks and springs, but wouldn't really say its heavy.
Maybe its not really that heavy you just need to get used to it.