We traveled south on the Cassiar last summer(early August) and found some construction but by and large, no problem. Still some frost heaves but they pretty much fix the more severe ones by mid summer. That's why I recommend coming back that way late in the summer.
If going to Stewart/Hyder(what a beautiful drive), just past Hyder is some good bear watching and Salmon Glacier is an great toad ride and an incredible view of the glacier.
Travel east on Hwy 16 to Prince George was good with very little road work...but of course, the harsh winters make all this subject to change. Bob
BTW, we drove from Whitehorse down to Dease Lake and stayed at Mountain Shadow RV right on the lake...beautiful CG with an even better view. Also, unless you want to stay in Hyder for a few days, I'd recommend staying on the Canada side in Steward(we stayed at Bear River RV, nice park - laundry room, not so much), it may save some hassle at the border, much easier crossing in the toad. Oh yeah, Bear River is an appropriate name for the campground...not recommended to take after dark strolls.