I don't know exactly how many Pokémon got Defog newly this gen, but I know some other Legendaries like Yveltal, Reshiram and even Silvally got it. Here is an alphabetic list of all Pokémon that get Defog in SOME way:
Aerodacty, Altaria, Arceus, Archen, Archeops, Articuno, Beautifly, Beedrill, Blaziken, Braviary, Butterfree, Carnivine, Castform, Charizard, Chatot, Chimecho, Combusken, Comfey, Cottonee, Crobat, Cryogonal, Cutiefly, Dartrix, Decidueye, Delibird, Dragonite, Drampa, Drifblim, Drifloon, Ducklett, Dustox, Emolga, Empoleon, Farfetch'd, Fearow, Finneon, Fletchinder, Fletchling, Florges, Flygon, Fomantis, Giratina, Gligar, Gliscor, Golbat, Hawlucha, Ho-Oh, Honchkrow, Hoothoot, Hydreigon, Illumise, Kartana, Klefki, Landorus, Latias, Latios, Ledian, Lugia, Lumineon, Lunala, Lurantis, Mandibuzz, Mantine, Masquerain, Mew, Moltres, Mothim, Murkrow, Ninjask, Noctowl, Noibat, Noivern, Nuzleaf, Oricorio, Pelipper, Pidgeot, Pidgeotto, Pidgey, Pidove, Pikipek, Piplup, Prinplup, Rayquaza, Reshiram, Ribombee, Rotom, Rowlet, Rufflet, Salamence, Scizor, Scyther, Seedot, Serperior, Servine, Shiftry, Sigilyph, Silvally, Skarmory, Skuntank, Smeargle, Snivy, Spearow, Staraptor, Staravia, Starly, Stunky, Swablu, Swanna, Swellow, Swoobat, Taillow, Talonflame, Tapu Fini, Tapu Koko, Thundurus, Togekiss, Togetic, Torchic, Tornadus, Toucannon, Tranquill, Tropius, Trumbeak, Unfezant, Venomoth, Vespiquen, Vibrava, Vivillon, Volbeat, Volcanion, Volcarona, Vullaby, Whimsicott, Wingull, Woobat, Xatu, Xerneas, Yanma, Yanmega, Yveltal, Zapdos, Zekrom, and Zubat
