I suspect that is a rendering issue. I guess they could go with dark glass for the top but it doesn't make a whole lot of sense. As I mentioned a while ago, there is a similar canopy for the Seattle convention centre that has tall buildings on either side. I was there on a fairly cloudy November day (practically identical to the kind of November days Halifax gets) and it was fine.
The towers remind me a bit of the Eaton Centre towers in Toronto (250 Yonge St), which look okay, although the newer one of those is from 1992.
Here's a decent aerial from 2006 that shows the site. I think it would actually be very interesting to have buildings like that farther up the hill. They would make the city feel a lot bigger. I would like to see a bit of a re-assessment of what is 'downtown' Halifax -- the city is growing and the 1950 idea of having major commercial buildings below Barrington or whatever is out of date:
Why can't the city grow and evolve so that all those blocks are considered the 'CBD'? Argyle Street is nice, yes, but there's also Spring Garden Road, Gottingen, Agricola, Quinpool... why does the city have to remain static?