Well viable builds hmm.
Caster builds: EK, Freezing Pulse, Fireball/burning build, Detonate Dead+Firetrap build, Trapper, Summoner, Discharger(few variations but let's put them all as one), Molten Shell+Tempest Shield caster tank, Incinerate, Explosive Arrow(technically uses a bow but pretty much a caster build), Dual Totem(as a general playstyle, the spells used can vary a lot and will affect the build a lot)
Ranged attack builds: Wander, LA chain, Ice Shot pierce, RoA(there's 2 big variations, phys and elem), Split Arrow crit phys, Split arrow cast on crit hybrid, Burning Arrow avatar of Fire burning build, Aura support builds(which tend to be wander/bow builds, 5-7auras, conduit with frenzy/powercharges/enduring cry kind of stuff).
Melee builds: Leap Slam 2H, Spectral Throw 2H, Spectral Throw 1H Dagger(with a cast on crit variation but tend to be fairly similar), Cyclone dagger cast on crit hybrid, Infernal Blow(weapon or fist variation), Dual Strike splash, Double Strike splash, Reave dagger/fist, Ele cleave(way nerfed, still does as much DPS as a caster build), Ground Slam, Sweep, Lightning Strike dagger, Dominating Blow, Flicker spam.
Maybe forgot a few builds, but that's a pretty good list. There are a lot of notable skills that are not used in any particularily viable builds or only used a secondary skills. The change to dot scaling might make them a lot better though(puncture, poison arrow, viper strike come to mind). All these builds are viable in endgame, they don't necessarily perform at the same level so there's various tiers, but they are able to clear any content provided they're sufficiently geared, at an acceptable pace. A lot of these builds also have multiple variations on their defense type(IR for armor, evasion+acro, life or CI etc). Most of them are viable on Hardcore but some require specific reworking to counter the downsides of the build(for example molten shell/discharge builds will want to get vaal pact if they don't want to one shot themselves on reflects).
If I go through the list of active skills you can design a build around(so not like Anger or Rejuvenation totem), there's very few skills that I think you can't build efficiently on.
Str: Everything usable but Searing Bond(shouldn't be an actual totem but a support for totems) and Shield Charge(clunky to use as damage, poor damage, poor aoe, outclassed in every way by leap slam as a movement ability). Heavy Strike and Glacial Hammer a bit weak, Heavy good as secondary for single target 2H melee, Glacial can do interesting aoe freeze builds but damage output is poor.
Dex: Elemental Hit I'm not too sure there's a very good build for it with all the elem nerfs, Poison Arrow lacks scaling, Puncture ok damage but technically only really usable with a bow and damage over time isn't that high compared to just shooting the mob more so fairly pointless, Viper Strike not scaling enough and no aoe possibility but really good at boss killing, Whirling Blades terrible at anything but movement, which it's ok at but Leap Slam is better in some situations(less desync when crossing tight passages, can jump over obstacles). The degen scaling patch should be coming next week or in the next major patch in 3weeks depending so it'll probably help 3 of these skills a lot.
Int: A fuckton of unusable primary spells, due to terrible scaling. Arc poor damage, Arctic Breath poor damage(but utility in the form of chilled ground, nice for a totem), Fire Storm randomness, requires mobs to stand still, kills you instantly on lightning thorns, have to choose between high single target damage or large aoe but terrible damage on a single point, Ice Nova still scales like shit, Ice Spear clunky mechanics when cast by the players, works alright as dual totems but freezing can be done more reliably with cold snap traps or freezing mines and damage is awful, Righteous Fire maybe overnerfed, not sure with new Purity aura, Shock Nova awful design with the deadzone, great at applying shock stacks with high quality however, ends up being a good secondary and awful primary.
