avenger warder/archon
ex [1.1.9.0] 2H Avenger Archon Callagadra kill 2m50s, Ravager kill 1m40s, Mogdrogen kill 1m55s, Crate of Entertainment kill 1m, SR 75~76 easy farm[vid]
auto attacker dervish or blademaster can also be pretty light on buttons, depending on what type of content you want them to do
suppose you could do an “unoptimized”/lazy cadence death knight
likewise on a blitzer or skater
shadowstriker is fairly few buttons, but not necessarily “casual” because of its squishyness so the support/“oh sht” buttons might be stressful in some situations
forcewave spammer, if you can accept the limited content you can make it fairly tanky and 1button’ish, tho it might not exactly rock your world from excitement