There are several primary issues to why Wulfric is a joke of a Gym Leader.
1) He lacks a Mega Evolution to use despite the player having access to them
2) He only has three Pokemon despite it being expected of players to have nearly fully or full teams by this stage in the game
3) He has no way to counter Fire-Types which given Delphox, Talonflame, Charizard & Pyroar as well as numerous other Fire-Types available later in the game leaves him very easily countered by the player almost from the start of the game.
4) His ace Pokemon is a terrible Pokemon due to how utterly slow it is and its terrible Sp.Def stat.
Personally if I was to give Wulfric a team it'd be;
1) Abomasnow (Mega) [Lv52] - Blizzard, Wood Hammer, Ingrain, Rock Slide
2) Lapras [Lv52] - Hydro Pump, Ice Beam, Thunderbolt, Swagger
3) Vanilluxe [Lv53] - Freeze-Dry, Water Pulse, Double Team, Flash Cannon
4) Mamoswine [Lv53] - Earthquake, Icicle Crash, Thrash, Stone Edge
5) Aurorus [Lv54] - Freeze-Dry, Psychic, Thunderbolt, Earth Power (cheating a bit on this since it's an ORAS tutor move)
I have no idea why GF thinks limiting the Gym Leaders to three Pokemon is the way to go imo it should be 2|3|3|3|4|4|4|5 also this way he has a variety of secondary types thanks to Lapras' Water-Type, Mamoswine's Ground-Type and Aurorus' Rock-Type. I'd also go with Aurorus over Avalugg because of the aforementioned god awful Sp.Def of Avalugg but also it's incredibly bad Speed, like Aurorus isn't fast either but at least it isn't so slow that Trick Room is the only way to get it to function, plus Aurorus is more evenly spread between Def and Sp.Def and has more in HP.