I dont have anything against crossbreds as in the working world we are not particularly focussed on breed purity, more on working ability, but good breeders know their lines.
On the subject of health, I have known good crossbreds but I have also known some very sad disasters, my friend had to put her little pet shop purchased crossbred down at age 3 from severe HD. My mothers rescue labradoodle cross maltese has always had a raft of heallth issues and has cost quite a few thousand dollars to deal with and continues. Other friends have had some serious temperament issues, one had a lab akita cross that was so aggressive it had to be put down at 12 months old as did the rest of the litter. I also had a friend who rescued a crossbred pup of unknown type and it died from a type of fading puppy syndrome despite the vets best efforts.
Not sayin that this doesnt occur in purebreds because it does. I know a breeder who doesnt test for PRA in her cattle dogs and quite a few have been euthanaised.
But the better you know your lines and what might be genetically incompatible the more likely you are to reduce these things. Knowing the lines whatever they are in the long run saves a lot of heartache, you can be sure of that.