And here's a third option.
This one should fulfill the latter part of your wish: "(and other tags)"
It requires two virtual tags:
virtual tag 1label:
TagToCheck<Album Rating><Album Artist><Album><Disc#>
virtual tag 2label:
Inconsistent album tag$If(<Album Track Count>=$Count(<TagToCheck>),,inconsistent)
Then set up a library filter or a playlist that has the rule:
Inconsistent album tag has a value
To define what tag should be checked for consistency over a whole album:
That is defined by the first tag that is listed in the virtual tag
TagToCheck.
So if you e.g. want it to check if the year is consistent for all tracks of an album, in the example given, change:
<Album Rating><Album Artist><Album><Disc#>
to:
<Year><Album Artist><Album><Disc#>
Or if you want to check if all album tracks are of the same audio coding, use:
<Kind><Album Artist><Album><Disc#>
etc. etc.