So Im currently Mawtribes and use a mixed list, mostly due to points but also because it's quite fun.
My LGS doesnt have a whole lot of armies or people that play, but they only just started with AoS a couple months ago, so the armies I play against are Khorne, Bonereapers, and Stormcast.
Mournfang are new to my army, only had 3 games so far with them. But they are not bad units.
The Riders with the club and fist are
3 attacks, 3+/3+/-/2 each
The mounts are
4 attacks, 4+/3+/-1/1
2 damage on the charge
Imo, they are a bit swingy, but can do a lot of damage on the charge. Especially after some buffs. Huskard on SH can make the tusks do 3 damage on the charge, and theres a butcher spell that adds 1 damage to all mount attacks.
Because who doesnt like mournfang doing 4 damage with the tusks and SH doing 5 damage with the horns.
Also in these games I used a Frost lord on SH once, and Huskard on SH twice. For just the mount, holy hell does it just delete a single unit. Which is where I believe it's meant to work best. They can also shrug off insane amounts of damage, that should kill them. And they have an artifact that let's you ignore your current bracket and treat the mount as having 0 wounds taken.
In short, SH are monsters and elite/hero killers. Less models the better. But a single 10 man unit of Skinks should not be able to hold off mournfang, especially if they charge.
But a 20 man unit should, which is the same price as 2 mournfang (140pts for 2).
Sadly in short, skinks are still the best and seemingly only option.