How many cap ships would it take to down the DS?

[Mad]

The Death Stars planetary shields are limited by its surface area. Putting such a powerful shield on something with that much surface area has its limitations. Because of this the concentrated form of power in the mini SLs on a Sovereign or Eclipse has a real possibility of being able to penetrate through the Death Stars shields and cause significant damage. You need not down shields in order to get through them.

You can't really say that, though, as we don't know how the shields are destributed. The shields probably projected by lots of deflector towers (ANH: "There's a lot of fire coming from the right side of that deflector tower") that channel the incoming energy to a high-capacity heat sink, or set of sinks. It's unlikely each tower has to shield an incredibly huge section.