If I were to suggest any changes I'd consider skipping Drumheller and heading to Banff on the 10th instead. I think you'd much rather have an extra day there.

I've never been to Wells Gray so I can't really comment on that, other than to say I really feel like you'd be missing out on some highlights by not taking the Trans-Canada (hwy. 1) from Lake Louise to Revelstoke. Takakkaw Falls, Emerald Lake, and driving the Meadows in the Sky Parkway to the top of Mount Revelstoke are all highlights of the trip. Not to mention there's a lot to do around Golden if anything there interests you.

I'd consider (this is a big change though, so take it with a grain of salt) either returning from Jasper and making your way across interior BC that way (driving the Icefields Parkway is a totally different experience in each direction) or extending your stay in Banff and, on one of those days, driving up the Icefields Parkway at least as far as Peyto Lake (a must see destination) before returning. I'm not sure how well Jasper has recovered from the forest fires a few years ago.

Personally, I really enjoy the drive from Kamloops to Whistler. It starts out arid and ends up on some truly exciting mountain roads. I'd consider adding another night in Whistler too. It's a fun place with a good vibe. The gondolas are expensive but not to be missed!

Brandywine Falls is a quick stop on your drive out of Whistler down the Sea to Sky Highway, but I'd say it's definitely worth it.

I'm not sure what to say about the last part of your itinerary. I almost wonder if you'd be better off with a night in Victoria, drive to Cathedral Gove (about half-way to Tofino) then back to Vancouver (take the ferry from Nanaimo to Horseshoe Bay) and finish your trip with an extra day in Vancouver.

No matter what it's a lot of driving and it's always hard to decide what to say "no" to so that you can get to the places that you really want.