OOCSS: Is this broken down too much?
This is mostly a personal issue. But, in my opinion, there are 2 issues that are going wrong in your approach.

Making your objects reusable (The main issue in the DRY principle)

In my design, I want to have say 3 designs for boxes. Then, I spend sometime designing them. (that is, creating the style in the CSS). Then, when creating the HTML, I reuse that designs.

In your system, every time that I create a box in HTML, I have to re-design the box 

&lt;div class="box round gray darkshadow redtext"&gt;


At best, you will end copy-pasting the box from the previous page.
At worst, your web won't have a consistent look.

Hardcoding your style in the HTML

What should your CSS provide you ? The power to change your gray web, that is no longer fancy, to a blue one, without modifying your HTML. But, if your elements have a class that is gray, you will end with:

.gray {
    background-color: blue;
}


That, of course, will work; but won't give you an easy time understanding what is going on