In php methods grow in size, as do the quantity of params required.
Is it possible to get PhpStorm to auto-update the previously generated PHPDoc above the said methods, instead of manually writing the additions/subtractions...?
Nope -- no automatic updates without user consent.
Similar kind of request -- check the dev's comment.
You can place caret in such PHPDoc comment (or, better, on such new/additional parameters), press Alt + Enter (or via light bulb icon) and choose appropriate quick fix entry there.
This will work if appropriate inspection is enabled (should be by default) in PhpStorm settings (Settings/Preferences | Editor | Inspections | PHP) -- look for PHPDoc section (hint: also try search box).