arguments could be highlighted and validated. So,

@param name of argument

name could be highlighted in the method argument colour. Once @param was typed,
code completion could be used to get name for the list of the method arguments
below. If name was not in the method argument list below, then it could be given
a red squiggle indicating an error. Clicking on the @param could highlight those
parameters that are not yet documented. The same could be done for exceptions.

Code completion could also be used to ensure that class and method
cross-references are inserted correctly. I'm never entirely sure if I have
cross-reference syntax correct - I'm sure I'm not the only one.  Also, these can
 become silently invalid by subsequent code changes.

A further JavaDoc help would be if there was a keyboard/menu shortcut that
set-up @param lines for all arguments, @throws for all exceptions and @return
and stepped you through each entry in much the same way as happens with code
templates.