Well, what you have now in Diggles is emergency healing. Sure, it gives you a debuff, but that's still risk-free healing on a vampire. Thus, you leave them for later, and on the deeper floors it becomes a non-issue with your sparkling attack (non-melee healing, duh) and with maxed Killer Vegan (for as long as you don't try to heal every 10 turns).
Yeah, definitely grab Corpse Drinker for out-of-combat healing, but then I'd rush Veganism. The sooner you can get your hands on Level 5 Vegan's delicious, delicious +4 , the better off you'll be. And +5 is nothing to sneeze at, either. After that, yeah, Unarmed is a good plan for boosting your crossbow/throwing damage, unless you want to go more gishy and kill all the animals with Arctic Vortex? Wouldn't suggest it though.
Be sure to take at least a point in Unarmed for the knockback attack early on. It carries the early game.
Well, I finally get around to playing my Vegan werediggle and apparently some oddity with Steam Cloud or mistake on my part torched the save...so that was a thing. Next try: Fleshsmithing Wand Lore Egyptian Magic Archaeology Fungal Arts Swords Big Game Hunter Egyptian Magic would appear to be a total dud. No way I can support the mana requirements. Thinking Fleshsmithing for the heal, then Fungal Arts for the pet and consumables, then either Wandcraft or Swordplay, or rush BGH to the Diggle horde and build up behind that.
Actually, yes, you can. Start off with one point in Fungal Arts for the summon, then take Big Game Hunter for meat (because you will want to get Lure, and thus you might as well get the item-spawning first tier early), and then one point in Egyptian Magic (for trap detection). From there, you have a few routes, but the one I would go is 2 more points in Fungal Arts, 2 points in Archaeology (duh, I don't like it but a necessity is a necessity), 1 point in Fleshsmithing for additional (and likely redundant heal; we will want to get the Fleshbore sometime before the next century though so it's no big deal), then 1 point in Egyptian Magic, 1 point in Big Game Hunter, Fungal Arts to the captsone, Egyptian Magic to the capstone, then Wand Lore to the capstone and Big Game Hunter ditto. You might want to fit one more point into Archaeology at some point to get experience for those unneeded artefacts, too. And swords will get left out, but since you get piercing damage bonuses from Big Game Hunter, it's not a big deal. Because of Big Game Hunter's bonuses and both Lure and the horde of diggles (Release the Hounds) to control the monsters' movements, combined with ridiculous healing potential of your character (food, shrooms, flesh knitting, coral wands, the Nile, and later possibly meat shield with health regeneration) and the bag of tricks you have in Wand Lore, it really is difficult to die unless you run into a named monster or a monster zoo. And because you can use Fleshbore on named monsters (and Lure too, for added bonus) and ought to have even the weakest projectiles because of Fungal Arts (and the charlemagne from Archaeology, which should be decent because it's a pretty wizardly build), named monsters can be won against; similarly, because you aren't really using mana for anything other than your buffs, you ought to have a lot of mana mushrooms to spam that one attack skill from Egyptian Magic when you find a monster zoo.
Brilliant, Kazeto. I was looking at that set trying to find a decent strategy, and you pulled one out like BAM! Mad props.