So after doing the wiper dance for a bit, and I believe the tip came from either the mothership (tesla.com's fora) or here, I bought a bottle of
this, mixed it with distlled water, replaced the Bosch wipers that weren't working appreciably better with Costco special $6 blades (Michelin or Goodyear or whatever they always have and occasionally put on sale), and go figure.
Suffice it to say the result was like night and day. Zero streaking, with some of the cheapest wipers available. Which have held up surprisingly well, I might add.
That additive plus distilled water was the missing solution, no pun intended (okay, somewhat intended) that has been missing since 12/26/2014 when I began this silly odyssey with the first chariot. Terrible wiper coverage since day 1, both cars, no matter what wipers, no matter how many adjustments, and don't even get me started about the AP2 wiper features - laughably useless and verified yet again just this past week when there were Ark sightings here in SoCal.
Give that additive *and distilled water* a shot if throwing the more expensive wipers at the problem doesn't work out.