Hey Guys,
I noticed a few CSS conflicts with various themes like twenty twelve and the required and password classes used within the html. In twentytwelve and other themes it turns the text red. You get around this at checkout by specifying the text as black using edd-input alongside that class. I suggest either prefixing the classes like edd-password and edd-required or adding the edd-input class alongside. I think it would be preferable to prefix those classes.

I also noticed the legend tag is seemingly improperly wrapped in a span tag. Is there any specific reason for this?

I completely agree on the class, though we'll have to be careful about potential backwards compat there. Since it's a small class that is rarely styled directly, it's probably safe to change.
For the legends, see #3568
Good to know the legends is already on the radar. I agree, some themes may already have those classes styled, hopefully minorly only though.
I'm going to tag this for 2.6, same version as the legends issue is tagged for.
In 2.6.5 the <span> will be removed from the <legends> with #4540
When updating the required class, the JavaScript will also need updating as we reference the required class throughout the checkout JS
Merged into release/2.7
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2.6.5the<span>will be removed from the<legends>with #4540