I've never been to some of these more popular waterfall hikes on the Oregon side of the Columbia Gorge, probably because they just seemed like busy spots and short hikes.  While it's easy to see that they get huge amounts of traffic, early morning mid-week was a pretty solitary time for them. I combined some exploring on the Gorge Trail #400 and the Historic Columbia River Highway State Trail to increase the distance. It's a really nice casual mostly loop if you park at Wahclella and then travel take the HCRT to Elowah Falls parking and check the falls there and head back on the #400 trail segments, about 9 miles (not including visiting Wahclella). The falls are incredible and the trails to them explore some really neat canyons cut into the lava flows layers.