Hi there. For this pic, I think HDR may be unnecessary as the EV range may not be that dynamic to justify treatment in HDR; simple PP in Photoshop or ACR will do just fine...well, that's if what you're after. Second, I think you may need to do some sharpening after merging as part of your PP workflow. Compositionally, sorry to say this, but there nothing very interesting about this shot.
As for whether it is over- or under done HDR, I'd really say that it is about one's preferrences and "style", and it also depends on the context of the picture or message that one wants to bring out. It's just like a piece of canvas - you decide on the colours, brush strokes, etc. to bring out the essence of your work.
Cheers! Shoot more, post more!