O well for him who lives at ease
With garnered gold in wide domain,
Nor heeds the splashing of the rain,
The crashing down of forest trees.
O well for him who ne'er hath known
In Wilde’s time,  Garnered  could be used to describe “stored” as well as “collected”–giving one the image of tax collectors, notoriously rich figure of older times. This image is especially emphasized by the use of “domain”, seeing that it is used to describe territory owned by people of power. 
 This line also intentionally creates a setting appropriate for the biblical allusions in this text, seeing that tax-collectors  were often used  in parables and teachings of the Bible.
Tristitiae