One can never go wrong with Ringo Shiina, Cocco, Chara, and fra-foa
They make life worth living.
Try revisiting the former queen of J-rock, Nanase Aikawa, if you haven't yet. Gone were the days when artists of her caliber reigned supreme
All we have nowadays are Johnny's J-groups!
Hikki has one exquisite pop/rock song from her Deep River album: Uso Mitaina I Love You. Hitomi has a lot of wonderful pop/rock songs that are quite similar to Ayu's stuff. Try her Love Life and huma-rhythm albums. Or just buy her singles collection: Self Portrait. I also slightly prefer Tomoko Kawase's material with The Brilliant Green to her Tommy songs. Try Love Psychedelico, Judy and Mary, and Luna Sea. Would you be interested in older J-rock? (from the 70s and 80s). How about progressive rock like Radiohead? If you do, I'd recommend Supercar and Miki Furukawa's solo album, Mirrors.
I don't like most of visual kei either, so I didn't include any here