After his excellent portrayal of JFK - I remember watching it as a kid and being wicked impressed - Devane must have been in demand for big ticket projects. Sadly, he didn't get very good guidance in choosing the right parts, an often overlooked aspect of the entertainment business....to Knot's Landing's benefit, of course...
Mack was the show's moral compass and his groundedness complimented Karen's hysteria perfectly. Also, Kevin Dobson was the best looking male cast member with a huge fan base. He was never going to be killed off...