Intimidate is a great ability for Luxray, despite his rather average defensive capabilities. A few useful resistances allow him to take quite a few hits before fainting. When factoring in Intimidate, Luxray is capable of surviving Swords Dance-boosted Bug Bite from Scyther and Stone Edge from Kabutops to hit them back with Discharge. Unfortunately, with the removal of Crobat, Honchkrow, and Staraptor from the UU tier, this set has lost some of its relevance. Still, he makes a decent switch against physical Water-types, Scyther, and Swellow, while keeping the useful Electric-type STAB and acting as a status platform.
Toxic cripples walls, while Discharge has a chance to cripple fast sweepers with paralysis. Thunder Wave is an option over Toxic if you prefer a more reliable way of spreading paralysis. Thunderbolt is an option over Discharge if you are using Thunder Wave, or if you don't want to accidentally paralyze something that you want to poison with Toxic. It also has more power, but against the aforementioned threats, both are equally good. Luxray's support movepool is lackluster, but Protect works nicely with Toxic and helps recover health, while forcing Swellow to take another turn of poison or burn damage if he tries to use U-turn to escape. Roar is nice on any defensive Pokemon, but has poor synergy with Intimidate.
This Luxray set faces competition from Arcanine's defensive set, which works similarly. Arcanine may seem to overshadow Luxray due to the advantages of Morning Sun, Will-O-Wisp, and more powerful attacking choices; however, Luxray's two move coverage, Thunder Wave, and lack of a Stealth Rock weakness allow him to do some things that Arcanine can't. Crucially, Luxray can take on physically based Water-types, while Arcanine cannot.
Again, Luxray needs teammates to take Ground-type attacks. Entry hazards support this set well if you're using Roar, so Cloyster, Omastar, and Qwilfish are good considerations to lay down Spikes, while Stealth Rock users are plentiful. Dugtrio doesn't OHKO this set, but Luxray cannot OHKO him either, so having something to lure and deal with Dugtrio is also very helpful. This set counters physical Water- and Flying-types, so Fire-type sweepers like Ninetales, Houndoom, and Moltres, who fear users of Aqua Jet and being revenge killed by Swellow or Scyther, are ideal teammates. While adding more Pokemon to your team who are liable to getting trapped by Dugtrio may seem like a bad idea, equipping Ninetales or Houndoom with a Shuca Berry or using Sucker Punch on Houndoom can give Luxray the Dugtrio lure he needs.