The dangers at Whytecliff are much the same as at any other dive site. Current can be an issue, particularly if it hasn't been planned for. Low visibility can be a problem just about any time of the year, but more in the summer. Depth can also be an issue when diving off the islet or the cut. Logs and other debris are fairly common, especially in the fall or winter when we've had heavy rain. Boat traffic can also be a consideration when diving around the cut - easy way to get a Yamaha haircut when boaters are coming too close to the park boundaries. For that matter, I've even seen boaters & jetskiers INSIDE the bay - not common and mainly because of ignorance, but still a hazard when we're used to not having to worry about it.
I don't think Whytecliff is any more hazardous than Porteau Cove. If anything, the vis and currents can be worse at Porteau. The artificial reefs at Porteau also pose a risk of entrapment, and need to be treated with respect. Depth can also be a problem at Porteau Cove, although not in the same class as the walls at Whytecliff. The bottom at Porteau starts rolling off fairly quickly once you get out past the marker buoys, and a strong tidal current could easily take you further out if you're not careful.
All of this stuff is just part and parcel for diving - the key is to plan for it. Current is fairly predictable if you check your tide tables and avoid diving during peak tidal exchanges. Poor vis requires stringent buddy contact procedures (stay close & plan to surface if separated.) Depth means that you've got to plan your dive for an appropriate depth and then have the buoyancy skills to dive your plan. You can plan for logs & boats by checking out the site at the surface before you dive, and paying attention when you're surfacing (listen for boats, look up to make sure that youre not surfacing under something.)
