Well, let's go through a build here real fast...

http://www.diablofans.com/builds/66584-quin69-gr69-hammer-crusader

Top rated crusader build for the month according to that site.

It has a full light set, which makes hammers have a 750% damage bonus and lets you do 500% extra damage falling swords a good bit more frequently. There's also some timed damage reduction, but that's fairly trivial. There's also another ring you'd be losing that cycles through elements that adds up to 200% extra damage. Reading into it, elemental damage and bonus skill damage is additive, so you are doing an extra 950% damage with hammers and 700% damage with fallen sword (assuming the ring is in tune).

Let's be generous and say with this build you get to use falling sword every 4 seconds for 1700% weapon damage and that multiplies with the 700% (8x total) extra to make it do a total of %13,600 weapon damage.

Meanwhile blessed hammers will come more frequently dealing its 320% * 10.50 for a total of %3360 weapond amage.

That might seem like a lot, but... assuming you just change the set item and don't even replace it with legendary powers, if that 9600% extra damage is multiplicitive and not additive, your blessed hammer damage is already going to be %320 * 97 or %31,040 weapon damage... that comes out far more freqently than the fallen dword above doing nearly three times as much damage with larger AOE.

I figure I have to be wrong on at least one of two things... possibly, the item description on the website is just wrong right now and the Blizzcon figures someone else cited are correct. Alternatively, maybe it just gets added to the bonus weapon damage from str rather than multiplied like bonus skill damage.