Helltooth uses Grin Reaper, it's core. It's cubed though cause you need the Helltooth helm for 6pc without RoRG so you can use F+R. The mimics spam almost everything you have, firewalls, piranhados and acid cloud/zombie bears plus whatever your primary is, great stuff. You also have 15 fetishes from the Belt of Transcendence, so there's some pet aspect, it's everything WD in one build ^^.
Weapon wise, the easiest to obtain is Scrimshaw, because there's only 2 legendary spears available to WD, so upgrading rares obviously is super easy. Getting an ancient might take a bunch of tries, but it's better than pretty much any other class. Other good weapon is Suwong Diviner, but there's a lot of garbage staves for upgrading making it hard to get. They use different dump spells so depending on your tastes, you might want one or the other. Other than these, really any weapon will do, the strongest the better. Maximus might actually be kinda good since iirc it rolls fire% which is good for firewall.
Also I know you said it's an alt and shit, but at least pick a 4th passive ^^. And use anything but Cindercoat? It doesn't cube the fire dmg, only the ressource cost reduction, and firewall doesn't cost any mana.
