This usage of 'well' is not the intensifier usage, as Dwight Bolinger argues in 'Degree Words':
In dealing with degree words and the comparative indeterminacy of
'approval' and 'fulfilment' [though 'well-spoken' obviously carries the approval sense
and 'well-read' obviously carries the intensifier sense , what does eg
'She baked the bread well' mean?], it is well to remember that [words
which cannot be intensified can accept only the 'approval' sense]
It was a well-conceived plan.
The case was well argued. [both mean 'in a good way' not 'thoroughly']
This is equally true when ['well' is used with] forms other than
verbs, though these are less numerous; semantically, they are very
much like verbs:
We are well rid of them....
For 'well rid of', some speakers would use 'well shut of' with 'shut'
used as a verbal ['well shut of' best regarded as colloquial (but
quite common) in the UK].
He is well rid of them uses 'well' as an evaluative pragmatic marker (a comment by the narrator on the value of the fact that 'he is rid of them'). Traditionally, this is a one-word reduction of a comment clause, or a[n evaluative] sentence adverbial. It is paraphrased by 'It is well that he is rid of them' (archaic) or 'It's a good thing that he's rid of them'. The usage is not the intensifier usage of well seen in say 'He is well clear of them'.
The usage is unusual in that evaluative etc pragmatic markers are usually set off by commas to distinguish such usage from the adverbial one:
He is happily married. [adv]
He is, happily, married. [pm] (cf Happily, he is married.)
He is, happily, well shut of them. [pm]
but He is well shut of them. [pm]
shows that 'well' bucks the trend.