Yes, Saurus heavy armies will have great difficulty dealing with the new Dark Elves. However, it is not nearly as difficult to adjust your strategy when facing Dark Elves, as they did not gain the benefit of ASF. Hatred is an amazing ability, but it can be more easily exploited (think sacrificial skink units) to draw the DE out of position.
Big things to be wary about are the new shades (which can wield GW or double HW), and the power dice potential of even the lowliest of sorceresses.
That said, the biggest thing to worry about, and where the Dark Elves will gain their greatest strength from, are their magic items. The Ring of Hotek now is protects everthing within its range rather than just the bearer. The Dark Elves have a ward save that is made if the roll is below the attack's strength. There is a cloak which has a bound steed of shadows. Then there are a myriad of new items that can potentially change a game such as Hydra teeth and a number of new banners (think ASF, and no stupidity for cold ones). Oh, and there is a dagger that can be used to sacrifice your opponents own troops (mmmmmmm)
The nature of the Druchii has not changed, so shooty/magic armies will still not be nearly as effective as the mobile assault forces. The problem simply becomes that now every unit is better at its job, meaning that the Druchii are no longer the finesse army of old

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