DV codecs are all the same, and they are all lossy and horrible for text. The first question you need to answer is "How are your going to use this video?" Answer that and we'll have some solutions for you. For now, render to a lossless or nearly lossless format like Animation Codec QuickTime or Motion Jpeg with quality set to about 90%, then compress using Adobe media encoder for delivery. I can't tell you what to use for your delivery codec because I don't know what you're planning to do with the video.
Has After Effects been known to cause video degeneration when rendering out using the same video settings that the video already has?
AE never renders to "the same video settings". Unlike editing programs it doesn't do any pass-through/ smart adaptive rendering. Each and any bit you do in AE will decode the source fully to RGB and any compression thereafter is a completely new encode. Because of that, any artifacts that already exist in the source become valid pixels and will cause more artifacts. And not to state the obvious, as a compositing tool AE isn't meant to generate optimized compressed output formats. You'll have to do some reading up on compression formats and CoDecs. And Rick is right - among compressed CoDecs, DV/ HDV has always been among the most awful, so avoid it at all cost. Even considerably compressed H.264 looks a lot better, but simply learn to use intermediate formats such as QT clips or image sequences for your work...