Can someone esplain to me damage stacking?

TANK wrote:

I'm playing Witch Doctor, I have a weapon damage of 52, intelligence of somewhere around 600 and a damage rating of something like 525ish.

When i cast Gargantuan and he goes into rage mode, it says he does around 200% weapon damage.  So how is the damage he does calculated?  200% of 52 is 104 but then isn't intelligence suppose to also amp my spells?

I could use some help understanding how this stuff all stacks up.
                              

The buff is only affecting Weapon DMG after the fact.  So your weapon DMG goes up and any spells attributed to the weapon dmg are then buffed by your over all intelligence.  The DMG rating you see is the overall Damage Per Second that you're capable of doing.  

I've been confused as well regarding damage on my wizard. I find it odd that they are using weapon damage as a major component of overall damage. I also find it confusing how +damage and weapon speed buffs really play into casting spells. I know more theorycrafting will come out but for now it seems diffucult (for me at least) to figure out what the best mix is.