Blazing spiders & Leaping spiders, do they really deal ~600% weapon damage per jar?
No, they don't. They (Blazing) are listed as doing 156% damage overall, but after testing it with the DPS meter I'd say they are doing closer to 300%, which is still really good.Is this the best single target skill the WD possesses? (Besides perfectly targeted bears)
Nah, Spirit Barrage/Well of Souls is still better. Blazing is competitive if you dump all your mana gear and focus on damage, but then you've hamstrung yourself from being able to use other high-mana skills like Bears or AC.
WoS does more damage, but the mana difference is the kicker for me. I don't really use corpse spiders for single-target damage anyway, i just spam them for longer elite encounters when i get low on mana. the damage/mana spent is incomparable.