How do you fight against war machines? Chameleons cannot get in a scouting position unless your opponent practically gives you a spot to deploy behind lines. Terradons/rippers seem like the only answer, but more stegadons is where my $$ want to go. Are there any other ways to deal with these suckers? (In particular O&G war machines)
Skirmishers can work fine against warmachines it's just about how long it takes them to get there. Heavens magic is pretty much the only thing that makes this possible and keeps beasties alive until they reach combat. Tetto is a triple threat; drop comets, vanguard D3, and ice shard blizzard. I've run him and two other skink priests as caddies with ice shard and managed to not lose any models to war machines for 3 turns. The only downside is how awesome lore of beasts is when used with EOTG and the monster mash. It's still just a 50/50 chance to shut it down with blizzard, but that's better than none. Also ice shard isn't totally worthless in cloes combat and it's up to you if you want to vanguard skinks to warmachine hunt or monster to get them to combat faster. Best of luck.
More often than not, I tend to build my armies with the goal of minimizing obvious war machine targets. Against Orcs and Goblins, you should never have a cowboy running solo (no look out sir against doom divers) and make sure your TG bunker or Cold One bus has a character with the Iron Curse Icon. Then magic softens the blow. For a comprehensive list of tips, check out the anti-cannon Tactica about everything works against Orc artillery too except turning dinosaurs sideways.
I've never really had a problem dealing with war machines with chameleon. War machines need to see you to hit you, so you should be able to see it. For catapaults etc, they sit higher and true line of sight comes in, you can see them easily enough. It's only the small ones like mortars that don't need line of sight to shoot that may be a problem. Remember, cannons still need to draw a line of sight from its spout to the point of the ground it wants to aim for. If it's not on a hill, it will generally only be allowed to hit the front rank of a unit (or before it), not the space behind it, as it can not see it.
I had a massive argument with an Empire friend a while ago about cannons and true line of sight. He thinks he can see the ground past the unit of Saurus. Technically you can see tiny bits of the board through them, but realistically a cannon would hit them, so he can't see behind them for the purpose of aiming. Also they would be moving and such. I would often have a unit such as Salamanders next to the Saurus so that he can't see the ground (let alone the Sallies). Also buildings are good for hiding a Steg behind if you can until the war machine is destroyed. Even if deployed in the front, Chamos usually get closer to the warmachine one turn before Skirmishers would
re: the tiny gaps between models: Angle the unit slightly. models will cover the gaps. Also, true line of sight means unblocked line of sight. So he can eat a cannonball sandwich hahaha
Somewhat related: Does stacking Iceshard Blizzard on a war machine mean that the operator needs to roll 4+ more than once in order to fire?
But doom divers and rock lobbers don't need los right? Heck the doom divers don't even care if you are in cc. For something like a spear chucka is los granted if you can see the stegadon flag poking out over a rooftop?
Every once in a while you'll run into someone that will try something to the effect of I can see the tail of your carnosaur past the building or his head above that building. I generally just avoid people that try to play that way during a casual game. But if he's insistent I always get some pleasure in pointing out the house rules to him. The model occupies it's base if you can't see that when I break out the laser ;no dice and buildings, forests and impassable terrain are treated infinitley high something that is popular in tournaments I frequent as well. I've seen rulings about seeing a spot through a unit go either way, but I always regard it as shady behavior if the cannon is on the ground or they aren't aiming at a large target.