This post concerns vehicles and the Grav weapons out there. To make sure my reading of the rules is right. This may be a big one...
(For Reference on the traits)GRAVITON PULSE
Instead of rolling to wound normally with this weapon, any fighter caught in the Blast must instead roll equal to or under their Strength on a D6 (a roll of 6 always counts as a fail), or suffer Damage with no armour save allowed; any vehicle caught in the Blast must instead roll equal or over the Toughness value of the facing hit on a D6 (a roll of a 6 always counts as a success), or suffer a hit to the Body with no armour save allowed. After the weapon has been fired, leave the Blast marker in place. For the remainder of the round, any model moving through this area will use 2" of their Movement for every 1" they move (note this affects all vehicles regardless of their Locomotive special rule). Remove the Blast marker during the End phaseCONCUSSION
Any fighter hit by a Concussion weapon will have their Initiative reduced by 2, to a minimum of 6+, until the end of the round. Any vehicle hit by a Concussion weapon will suffer a -2 penalty to all Handling tests until the end of the round.Assume your vehicle is hit by a Grav weapon. Now you test to see it it damages. To do that you must roll under the vehicles facing toughness to cause damage
"any vehicle caught in the Blast must instead roll equal or over the Toughness value of the facing hit on a D6 (a roll of a 6 always counts as a success), or suffer a hit to the Body with no armour save allowed" i.e roll over the vehicles toughness or suffer a hit to the Body with no save.
Therefore a larger vehicle with higher toughness will find it harder to resist damage so a Wolfquad is less susceptible to Grav damage than the Ridgehauler. (In Physics terms that actually makes perfect sense. Lots of complex explanations but basically the science says a smaller object can resist rapid changes in gravity than a larger one).
Now the actual damage part. The trait says it suffers a "hit". All Grav weapons, Pistol gun and cannon, have D2 so a hit means you roll two Damage dice and then apply the best one to the Body Location.
Now the Grav weapons all have Concussion as well so every Handling or Loss of control test will suffer a -2 penalty which make it difficult (assuming no Handling upgrades) for all vehicles to pass readily,exept the Walker, Outrider and Wolfquad.
Given all this I am right to assume that a Grav weapon has little problem hitting the Medium and Heavy Vehicles (Blast make it easier), a very good chance of causing damage (Medium and Heavy Customs Front Ridge Runners Rock Grinders and Ridhehaulers all need a 6 to avoid damage). Then they get two Vehicle Damage dice to roll and pick the best (two chances of a Catastrophic hit 4 chances of a Penetrating Hit and 6 of a Glancing). With all the medium and Heavy vehicles they have a decent chance of failing the Handling test or loss of control test (anything worse than a 7+ puts them below average of a pass making it more likely to fail and suffer the consequences which after Concussion all of them have).
All this results in your grav weapon having very good chances of causing Damage, a higher likelihood of at least Stalling the Vehicle and, in the case of a Catastrophic hit which will cause a Loss of Control test at -2 (plus other stuff). which then has a 1/6 chance of Rolling the mighty Ridge Hauler and Wreaking it regardless of its Save or massive Hull Points.
All this adds up to Grav weapons, with Graviton Pulse and Concussion, being a more reliable way of at least Stalling the monster trucks and possibly Rolling them.
Couple a Grav weapon with a fighter with a Flash Grenade Launcher and it is simpliciy to neutralize the largest Ridge hauler all game. No need to whittle down its massive Hull points if it is constantly Blind.
If you made it to the end of this wall of text congratulations.
Are there any gaps in my reasoning?