Most deepstrikes come turn 2, and in the Custodes case their "vehicles" are pretty bulky so if a table doesn't contain tall opaque walls, you can kiss your dreadnoughs goodbye. My only expectation is that the BS of the hammerhead remains 4+ so that it can only go down to 3+ with markerlights. Still, 3+ tohit, 2+ towound, instakill custodes' big units that aren't landraiders... It's gonna be painful.
Also as of the opponent will leave a deepstrike location next to their hammerhead/broadsides for melee blenders to go and be in charge distance. They're Tau, they can afford to stay back.