Confirming there are still the four soloable 38-39 down arrows at the same coords listed. Two are on the eastern side of the river and are lone creatures. The two on the western side of the river are a pair.
The single mobs still have a 13 minute spawn timer as do the pair. The trick is to only kill one of the pair. Then break off the attack so the other stops hitting you. The one you killed will respawn in 5 mins.