A great person has just shared shock dyno graphs http://www.rctech.net/forum/13878386-post1.html. I will try my best to explain it:
First, RC shocks have linear response even for tapered pistons as I said before, if they work for you great but I didn't find anywhere that they work and now there's proof that they don't work as advertised. With that said, until 2 stage pistons arrive at the 1/8th market we will have to tune to the majority of the track sacrificing low or high speed damping. If anyone knows of 5wt or less silicone oil say so (my 2 stage shock piston design needs it).
Something I've learned recently, it's good practice to have higher ride frequency in the rear - or vice versa - to account for the front tires passing first through surface irregularities. How much, that depends on the type of irregularities you find at a particular track.
Please check the pdf on that link, any question just ask here I will do my best to explain.

I've been researching the best possible RC shocks, if I scale down the racing shocks used in MTB and other motorsports there's one that stands out, GMade XD. I want to try them with dual stage pistons. They have the bladder out of the piston way, proper bladder design and available in different shock length and type. On the other hand, if I stay with linear RC shocks (current gen) doing every trick in the book (foam behind the bladder+unvented cap+x-rings) will certainly not be enough performance wise. You can't tune compression separated from rebound and that hurts immensely. Even if I further develop my piston shim stack design it would be difficult to find a range of oils and piston holes to make it work, right now I'm looking at 4mm x 4 holes to use something around 200cps oil.

Other thing I found to help lots when tuning shock package is to see the track surface making the suspension work and not the car making the suspension work, also each tire of the car carries around one quarter of a car's total weight, that's spring related not damper related. Stiffer springs than most drivers would use and pistons that are balanced front to back would improve lots on bump handling. Once again I will say that it doesn't make sense using smaller piston hole size in the rear end, nor using shock oil to change the rate at weight transfers side to side, that's why most cars have roll bars.

Quick list of what to change setup wise.
Use this list only after your car is maintained properly, corner weights are balanced L-R and chassis de-tweaked.

Intended adjustment ----------------------------------------- What to change/address

Change side to side rate of weight transfer(WT)-------------Roll bar thickness/pre-load
Change rate of front to rear or rear to front WT--------------Kickup and Anti Squat
Change bump handling-----------------------------------------Piston hole total area/ shock oil
Change grip -----------------------------------------------------Increase tire load by using stiffer springs or roll center change
Loss of grip/gain of grip through track temperature----------Change tire compound
Prevent traction Roll--------------------------------------------Lower suspension frequency
Unbalanced flight attitude--------------------------------------Chassis has wear marks?yes - higher ride height on affected side; No - balance springs
Front tires balloon and wear on the middle-------------------Increase diff oil thickness front and center, smoother throttle finger

Increase stability: acceleration--------------------------------Increase rear toe-in in; rear diff oil change
Increase stability: straight line/bumps------------------------Decrease front/rear toe-in; increase rear droop; front roll bar too stiff
Increase stability: braking-------------------------------------Increase rear droop; balance rear roll resistance; more rear camber

Increase response----------------------------------------------Firmer inserts; check for too low springs/roll bars; too much rear wing
Decrease response---------------------------------------------Softer inserts; too stiff springs/roll bars; excessive front/rear toe-in

Dealing with understeer
Decrease understeer: steering fades at corner entry--------Less toe angles; more front droop; check if the front suspension dumps - increase front roll stiffness; roll axis not balanced.

Decrease understeer: no steering at corner entry-----------Coming too hot to turn; too narrow front track width compared to rear; too stiff wheel/insert combo; too stiff front roll bar/springs; too much bump stops; lack of front toe-in/out; unsuitable Ackermann angle; front RC too high or too low; more front droop; wrong weigh bias.

Decrease understeer: mid corner-----------------------------Too firm wheel/insert combo; excessive relative front roll stiffness; excessive front toe-in/out; wrong Ackermann angle; lack of camber gain; front track width narrow relative to rear; might be bottoming shock(s); lack of droop.

Decrease understeer: coming out of slow corners-----------Too much WT front to back - less kickup/more anti squat; less front droop.

Decrease understeer: coming out of fast corners------------Front track width narrow relative to rear; thinner rear diff oil.

Dealing with oversteer
Decreasing oversteer: corner entry---------------------------Too much rear brake bias/drag brake; roll stiffness imbalance; rear roll center too high; too little rear droop.

Decrease oversteer: mid corner------------------------------Rear wheel/insert combo too stiff; excessive rear roll stiffness; rear suspension might be bottoming; lack of rear droop; very loose rear roll bar.

Decrease oversteer: corner exit------------------------------Rear diff oil too thin; too much anti squat angle; excessive rear roll stiffness; rear shocks bottoming out; too much negative camber; too little rear toe-in angle.

If the car snaps suddenly exiting corners the usual culprits are: rear shocks bottoming out; lack of droop/wrong droop setup; sudden change in rear camber, particularly the outside wheel; getting on the throttle too soon ("Too soon junior...").

If the car can't put the power down smoothly check for: diffing out, particularly the rear diff; excessive roll resistance; excessive anti squat angle; rear wheel/insert combo too stiff; rear shock damping too stiff; too much camber change in outside wheel.

Transitions
Understeer starting to transition then snap oversteer on power: usually caused by too little roll resistance, suspension bottoms out and jerks the car. Stiffening the front ARB will load the inside rear tire on acceleration (win-win), increase front roll resistance by means of roll center or CG.
If the suggestion above cures the understeer but the car still snaps then the car falls on the outside rear wheel, same fix as the front - increase roll resistance. Loose ARB might behave like this too!