Welcome to Circle! Glad to see another druid in the ranks. Tanith is awesome, and can be built with just about anything competitively. She works well In The Wild Hunt, and her spell Affliction works really well with Reeves of Orboros, so I would recommend them. As a ranged unit, they will provide a good balance to the otherwise melee oriented army.
You are right about Loki - that dude is a boss and the model is gorgeous.
I would however caution against two units of Skinwalkers. Doubling up is always dangerous, especially as you are starting out, in case the unit doesn't perform as well as you'd like. They are fine, and if you love them then go for it, but imo they are not great and you might find that you rarely want two units in a single list as you expand to New warlocks and configurations.
If I were to make a list like you describe, it would probably look like this:
conflictchamber.com/#c8201b_-0qg1ee4BgZ4M5j5j5j4S5s5f2N5ocp4U4WCircle Army - 75 / 75 points
[Theme] The Wild Hunt
(Tanith 1) Tanith the Feral Song [+31]
- Argus Moonhound [6]
- Gorax Rager [7]
- Loki [19]
- Pureblood Warpwolf [17]
War Wolf [2]
War Wolf [2]
War Wolf [2]
Reeves of Orboros (max) [16]
- Reeve of Orboros Chieftain & Standard [0(4)]
Shifting Stones [3]
Swamp Gobbers Bellows Crew [2]
Warpborn Skinwalkers (max) [15]
- Warpborn Skinwalker Alpha [0(4)]
Wolves of Orboros (max) [11]
- Wolves of Orboros Chieftain & Standard [4]
Shifting stones are generally awesome and highly useful. The war wolves combine well with both the Reeves and wolves of Orboros to add free damage thanks to sic em. I changed the wild Argus to a moonhound, which I don't love but it adds value to your ranged game in the event of stealth models, and the point you save allows the bellows crew. They can trigger prowl on Loki and Tanith, as well as block LOS if necessary.
I don't know your experience level with warmahordes, but I would always recommend some lower points games to get a handle on the models you own and the feel of the fact before you jump bigger, as well as proxying models before you make the purchase. Buyer's remorse is real.
Anyways, good luck, and let us know how it goes!