I think that NAV and price are important to the yield oriented investor. If the price drops a lot, the yield goes up a lot... and eventually, the entity will cut its dividend to the yield that it views as necessary to pay to attract investors and that will be less detrimental to its NAV.
I think that a security that can't maintain its NAV and price fairly steady over the long term is really giving you back part of your principal to maintain its current dividend. You are sacrificing capability to earn future dividends to maintain present dividends.
If a yield oriented security like DVY has been losing value as the Fed drops rates, you have to wonder what will happen when rates rise. I think that you have to throw in the risk of the market's response to the end of Bush's tax cuts, which would take out the 15% tax on equity dividends. The odds favor that they will expire as a democratic Congress is very likely to prevent the action necessary to continue them... and maybe the market has been anticipating that. Seems like a pretty risky way to get a 5% yield to me. I don't think that a little over 5% is rewarding you for the risk you are taking...
jmho
erryl