In a way, isn't that the "I Repelled A Chaos Invasion" experience? Get fucked up then slowly fuck them up at incredible loss to both sides?
I can't imagine anyone having any problems with the vanilla Chaos invasion. It's so easy the AI tends to beat them without you doing anything.
Chariots.
Seriously, how the bloody hell do you stop those things?
They tank enough hits a full army's of Quarreler fire will only kill off one unit at the most, and the rest of the incoming force of chariots rip through your lines easy.
Ah yes, weapons of mass Surtha Ek.
If you're using Dwarfs, your best bet is Gyrocopters with brimstone guns. Failing that, slayer spam.
However, Ironbreakers will also stop them. To some degree. Not that you really need to. IIRC, many Dwarf units have charge resistance anyway, making chariots kinda derpy against them.
Get lots of armour piercing stuff. The AI kinda cheats with its chariots in that it can spam a hundred move orders in a second, this allows them to basically disengage from anything. Something you can't really do unless you're seriously micro-ing your own chariots like a god.
With other factions, Chariots do really poorly against large sized units. This means horses, trolls, tanks, giants, heroes, etc. Dwarfs don't really have anything like that. In fact, Dwarfs also don't have anything with anti-large other than Slayers. So your only options are armour piercing or slayers. Good thing is that your armour piercing and slayers are really good at killing them.
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If you're fighting factions with lots of monsters or large units (basically everyone except Dwarfs honestly), you should bring brimstone guns. They're your best bet at toppling Giants, Araknaroks, Grail Knights, etc. Just be aware they will lose the air fight to almost everything. Including bats.
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Edit: Oh, there are also irondrakes with torpedoes. You could try those.