Plague of Toads is quite an interesting ability.
Pros:
- Very High Damage
- Very Cost effective
- Applies poison damage (for BadMedicine)
- Spammable
- AOE
Cons:
- Very short ranged/Unreliable even at medium range
- Expensive for a Primary (not sustainable without some sort of mana boost)
The runes generally change one of these properties - Toad Affinity "fixes" the mana, Rain of toad fixes the range, Explosive toads sacrifices the poison in exchange for more damage.
The key question is "When would I use toads over poison dart or spiders?".
Compared to Both Spiders and Poison Dart, toads have lower single-target damage, and much shorter range, so toads are a better option if you're able to be in the think of it and have enough damage for priority targets in your build and have some slack in your mana needs. In exchange, you get a lot more damage into groups.
If you can meet these requirements, Plague of toads will put out A lot more damage - you can reliably hit 3 targets in melee range, putting out 390% dps unruned to a splinter dart's 180%.
It synergizes well with Pet Builds, and with Bad Medicine (and Jungle Fortitude as well), which provide the sort of tankiness you need to stand toe-to-toe and spam toads and are easy on the mana. It also synergizes with Locust Swarm, which has similar strengths and weaknesses, Haunt provides some complementary single-target damage and Grasp helps bunch things up so you can land more toads, and with Soul Harvest/Fetish Ambush/Mass Confusions because you'll be in the right position to get a lot of value out of these PBAOE abilities anyway.
It doesn't synergize very well with Horrify, because the spell breaks up your packs of targets, nor with spirit barrage or acid cloud, because of the mana concerns.
Overall, it is a lot more awkward than darts and spiders does need a lot more support from the rest of your build, especially as the enemies start to hit a lot harder, but it does have some interesting strengths in specific sorts of builds.
This is easily soloable although which class you play and your playstyle can affect your success. As you've probably figured out, killing things and fighting in general is the wrong approach. To complete the Crumbling Vault and any of the timed achievements, there are only a few things which can help you:
Luck:
- As the dungeons are generated pesudo-randomly, if you get a bad layout, your chances of success could be greatly lessened. There's a bit of a pattern to the map layouts that you can sort of pick up (possibly even picked from a set of pre-defined maps? I only mention this because I've seen some identical layouts when re-rerunning certain dungeons).
- Running into some stall champions is also a danger to your success as wallers and jailers can stop you in your tracks and their presence is entirely random.
Speed:
- Movement speed perks are helpful.
- The use of your movement ability is also invaluable. To support the use of your movement ability, having resource regen and resource improving equipment and abilities is helpful. To this end, also go in with full resource.
- Don't stop. Avoid combat and run past everything. Having minions/allies and followers out before you enter the timed section is helpful because they can draw agro away from you.
- If you do get stuck in combat, for your primary and if needed secondary attack ability, something with knockback is invaluable as it can clear a path for you very quickly. It is also preferable that this attack have some kind of AOE to clear larger space at one time.
Power:
- High health, dodge and armor can make it easy to tank your way through without worrying about your health. Buffing these can greatly help survivability. I find dodge more useful as attacks that miss don't affect durability or require healing.
- High attack power can really help speed you up as being able to one-hit the enemies will make certain that moments stuck fighting will be brief. Note that your goal isn't to kill or even fight anything so it might be best to neglect attack if needed for these types of challenges.
- Being higher level helps a lot.
- Playing with a dex or strength focussed class makes a huge difference too. With a level 22 monk, I ran Crumbling Vault on my first try in under 2 minutes. I buffed dodge and ran like crazy, taking only 2 wrong turns along the way. Playing as a witch doctor is not helping your chances so you may need to rethink your equipment and abilities from what you usually use. For int classes, you may need to ignore your Int for these challenges and take the hit to DPS in exchange for Dodge/Health provided by Dex and Strength.
- In order to maximize damage and defense, learning the way that the game calculates them is very useful.
Best Answer
Its very viable, specially with the passive that slows enemies down when using arcane skills. Certainly helps with kiting on hell and inferno.