Rocky,
I don't know our correspondent's route, but I would assume that he will be using highway 43 to and from Interstate 5, as it is the most direct and likely fastest route from Phoenix. Otherwise, his choice would be to take highway 99 to Visalia, then west to Hanford or take Interstate 5 to Kettleman City, then north on 41 to Lemoore and east to Hanford. Both of these alternatives will add anywhere from 20-40 minutes of additional driving. (Yes, we sometimes need to allow for these inconveniences!)
I share your frustrations with Tesla in not building out their network in Idaho to accommodate destinations not on the interstates.
I must disagree that highway 198 is not a "major" highway. It is the access highway from Tulare County to the Coast and to Interstate 5 if heading north and to Sequoia National Park's southern entrance for those heading east. I submit that it is just as important to us out here as US12, 20, and 93 are for you Idahoans. California 198 is just not as long as those highways and has (as you correctly point out) Superchargers that are close enough but not convenient to Hanford or Lemoore.
I guess sometimes we just have to realize that Supercharger coverage will be spotty for those who travel on secondary highways (like highway 43) for any distance because those trips will be the exception and not the rule.
A parenthesis to our colleague from Phoenix: You might consider Supercharging at Enos Lane (just south of I5 on highway 43 for about 15-20 minutes before arrival. I would suppose that would get you enough juice to return back to Interstate 5 in comfort when you depart.