4-linking an item is much harder now.

This league i've never had better luck with fusings, I constantly get 4 links in 1-2 fusings and six linked this bow in under 20

For every player who 6links in <20 fusing, there's someone who needs 2000+.
At least according to this guy. ;)

Your examples are good for nothing. There's no proof because we don't know the full data.

Found 3 5Links already with 1 character <80 in Ambush. In Domination I found none. Found 6 Exalts in Domination, in Ambush I found none.

Looks like Exalts are rarer now, 5 Links more casual?
No, it doesn't. There's not enough data to proof this.