Nurglitch from this thread said:
I suppose it would make more sense to have them rammed, rather than
tank-shocked. But the likelihood of a Rhino running over a Carnifex is
33%, and the risk of the Rhino being immobilized, stunned, or destroyed
is 66%. Likewise a Carnifex charging a 12" moving Rhino has a 68% chance
of doing that sort of damage.
Don't get me wrong, it's
frustrating to see a 200+pt Carnifex get run over, but it's also fun to a
Carnifex get a free Rhino in its diet. So I disagree somewhat on the
notion of Tyranids having no way to prevent movement to contest
objectives. Like the multi-charges, it's mainly a tactical problem.
He said some other interesting things too, but that one kind of encapsulates it.
I think he may be seeing this through rose-colored glasses a bit. The Carnifex vs. Rhino matchup is the MOST favorable for the Nids (within the "MC" category, the Zoanthrope fairs better). And yet it still has a 1/3 chance that the 35 point Rhino will run over the (minimum) 160 point Carnifex.
Now, I fully recognize that the relative points values are not the ONLY factor at play here, and that from a "game theoretical" perspective it might, at times, be fully worth it to take that risk. But I think it's important to at least note the disparity. When you start talking about other match ups like Tervigons versus Baal Predators, etc... it gets much, much worse.
And the truth is that this is something that fundamentally disadvantages Tyranids. Every army with vehicles can virtually GUARANTEE that if they put a vehicle somewhere, the opponent will not be able to put one of their units there during the next turn. This is a fundamental outgrowth of the turn sequence, since you cannot shoot away a vehicle before you move across the space it once occupied. This is an incredible tool, that doesn’t rely on dice. You simply put a Landspeeder a few inches away from that Land Raider, and you KNOW it will not cross it. At the top of turn 6, when you control the objectives by one, and your opponent has a Baal/Rhino/whatever capable of tank-shocking and contesting… this is huge.
This is similar to the way in which the fundamental mechanisms of the game limit the utility of melee in destroying enemy transports. Lots of our units have anti-infantry guns, and relatively few have (effective) anti-tank guns. But imagine if we could first wreck a Rhino with Genestealers, and THEN unload on the Space Marines with our Devourer Gaunts. Or if instead of being able to simply walk away or shoot us from point blank range the next turn, units in a transport which is wrecked in the assault phase are automatically considered to be engaged with any units in base to base with their transport and must pile in with them?
Now, Nurglitch, I know your thoughts on destroying enemy units via disembarkation shenanigans, and I agree that it’s a great tool in our toolbox. I use it when I can. But even you have to admit that it’s sometimes difficult/impossible to pull this off against an opponent with a few spare neurons to rub together.
A unit like a Land Raider with Blood Angel Assault Marines in it is designed to work WITH the ruleset. The vehicle moves. The Marines disembark. The Marines shoot their meltaguns at an enemy transport. They kill the transport. If they don’t kill it, the Land raider, or a nearby Baal, or a far-away Rifleman help to kill the transport. Then the core rules allow the Assault Marines are allowed to assault the CONTENTS of the transport they just shot at. Which makes sense. After all if I just zapped your ride with my meltaguns, and you are bailing out the back… I’m going to charge you!
But apparently, if a unit of Genestealers is literally crawling ALL OVER your Rhino (and by all over I mean they are "in game" only contacting the front half of the Rhino, but are "theoretically" crawling all over your ass), ripping apart its tracks and yanking its crew members out of their hatches to be horribly dismembered… the passengers can simply stroll out the back ramp, turn, and flame/bolter you to bits while you stand there looking bewildered “Dang, the Assault Phase is done now, I guess we can’t kill those jerks.” (Or, in the native Tyranid: “SCREEECHKKKKK… Hissss…. RAWRRSSSEHHH!”)
So, what's my point here? I'm not sure I have one. On the one hand, I think it's somewhat silly to obsess about the many ways in which the Nids are "swimming upstream" against the way that most armies can use and take advantage of the core rules. On the other hand, it can be helpful to recognize these distinctions and, if possible, recognize other ways to make the rules work for us.
And it makes for interesting discussions on the internet, so... there's that.