I think part of it has been getting used to the Z. I don't notice the issue as much now...

I'll probably go with KW Variant3's and their lift deally, so I can handle steeper driveways and such....

I have this same problem and it is NOT normal. I feel that it is unacceptable for a car to behave like this. The car handles great in all other aspects, but this is downright unsafe. I've also driven many different cars with various suspension setups and I have never experienced this until I got the Z.

I have to agree to some extent. I am hoping the KWs will fix the problem when I can afford them. The effect for me is that the car feels much heavier than it is when canyoning.

i know what the OP is talking about first hand. my BC coilsovers can be set hard enough where it skids over the bumps..... great for a smooth track/street, but terrible otherwise. i keep it in the middle.....

sway bars made the confidence skyrocket. no more unsettled rear end, or body roll.

i do need the camber i think now.....with the hotchkis. at 90% they are great. but when i push the car hard, it slightly understeers on turn in, which quickly goes into snap oversteer if im not careful (rear sway on full stiff, which is too much, but helps the understeer on turn in).

i need to order the arms, but dont have the $$ right now.

all in all, id still say the oem set up is a GREAT compromise of the above.

SPL rear traction arms
 

Would the SPL rear traction arms help?

SPL RTR Z34

yes

Inexperience taught me to get aftermarket springs with stock shocks. Now i am feeling this effect very drastically (unstable on bumpy surfaces). I have the Eibach pro kit with stock shocks. Now instead of wasting money on those springs, ive read that you can order koni yellows and get them to valve them according to spring rates you give them. Is this true?

Yes, Koni offers custom valving, both fixed rates and adjustable.