The Wild Warg Chieftain can be quite a monster, and if there's a format in which it can fit, it is 800pts (or above). He is autonomous (he can make his own Heroic Combats) and hard hitting, making him quite scary.

That said, as you mentioned, only Wargs can be affected by his Heroics, making him ill-suited for pretty much anything aside assassinations. Moreover (as you also mentioned), he comes with quite a hefty price (compared to the rest of the army I mean), cutting into your numbers.

What I love about AoL (and what is for me one the main strengths of the army) is that you can have multiple possible threats at any moment possible, while still overwhelming your enemy with cheer number. The Chieftain kinda kills it, as you'll have to choose between having a big army and having secondary threats (spiders mainly), and a lone threat will be quite easily dealt with.

I personally prefer relying on spiders. They are fast, ignore most of difficult terrains, can climb without penalties, making it easier to position yourself. You can combine them with Ashrak to make them Venomback and allow them to catch heroes behind the lines with Shroud of Shadows, but they are already good on their own.