Hapatra and Nest of Scarabs do not trigger when token with wither or infect deal combat damage to a creature and die.
I have this output from when I cast Triumph of the Hordes and attack once with a token creature, and once with a nontoken creature. The attackers are blocked and die. Hapatra triggers for the nontoken creature, but not for the token creature. (Flourishing Defenses triggers for both).
11:20: Turn 16 wurst (34 - 35)
11:20: wurst draws a card
11:20: wurst puts Llanowar Wastes [23c] from hand onto the Battlefield
11:20: wurst plays Llanowar Wastes [23c]
11:20: Ability triggers: Evolution Sage [aff] - Whenever a land enters the battlefield under your control, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)
11:21: wurst loses 1 life
11:21: wurst casts Triumph of the Hordes [121]
11:21: wurst puts Triumph of the Hordes [121] from stack into their graveyard
11:21: wurst attacks with 1 creature
11:21: Attacker: Elf Warrior [a3d] (2/2) blocked by Terastodon [f4e] (9/9)
11:21: Elf Warrior [a3d] deals 2 damage to Terastodon [f4e]
11:21: Terastodon [f4e] deals 9 damage to Elf Warrior [a3d]
11:21: Elf Warrior [a3d] died
11:21: Ability triggers: Flourishing Defenses [1a6] - Whenever a -1/-1 counter is put on a creature, you may create a 1/1 green Elf Warrior creature token.
11:21: Ability triggers: Flourishing Defenses [1a6] - Whenever a -1/-1 counter is put on a creature, you may create a 1/1 green Elf Warrior creature token.
11:22: wurst creates a Elf Warrior [cff] token
11:22: wurst creates a Elf Warrior [95a] token
11:23: Player request: Rolling back to start of turn 16
11:23: Turn 16 wurst (34 - 35)
11:23: wurst draws a card
11:23: wurst puts Llanowar Wastes [23c] from hand onto the Battlefield
11:23: wurst plays Llanowar Wastes [23c]
11:23: Ability triggers: Evolution Sage [aff] - Whenever a land enters the battlefield under your control, proliferate. (You choose any number of permanents and/or players with counters on them, then give each another counter of each kind already there.)
11:23: wurst loses 1 life
11:23: wurst casts Triumph of the Hordes [121]
11:23: wurst puts Triumph of the Hordes [121] from stack into their graveyard
11:23: wurst attacks with 1 creature
11:23: Attacker: Evolution Sage [aff] (3/2) blocked by Terastodon [f4e] (9/9)
11:23: Evolution Sage [aff] deals 3 damage to Terastodon [f4e]
11:23: Terastodon [f4e] deals 9 damage to Evolution Sage [aff]
11:23: Evolution Sage [aff] died
11:23: Ability triggers: Hapatra, Vizier of Poisons [2a6] - Whenever you put one or more -1/-1 counters on a creature, create a 1/1 green Snake creature token with deathtouch.
11:23: Ability triggers: Flourishing Defenses [1a6] - Whenever a -1/-1 counter is put on a creature, you may create a 1/1 green Elf Warrior creature token.
11:23: Ability triggers: Flourishing Defenses [1a6] - Whenever a -1/-1 counter is put on a creature, you may create a 1/1 green Elf Warrior creature token.
11:23: Ability triggers: Flourishing Defenses [1a6] - Whenever a -1/-1 counter is put on a creature, you may create a 1/1 green Elf Warrior creature token.
11:23: wurst creates a Elf Warrior [a48] token
11:23: wurst creates a Elf Warrior [e0d] token
11:23: wurst creates a Elf Warrior [fc8] token
11:23: wurst creates a Snake [50b] token
The same happens with Nest of Scarabs and wither.
Hapatra, Nest of Scarabs, Corrosive Mentor (gives all your black creatures wither) and a black Insect token on the battlefield. When Corrosive Mentors attacks and is blocked and dies, Hapatra and Nest of Scarabs trigger. They don't trigger for the black Insect token.
The -1/-1 counters are placed each time, but Hapatra and Nest of Scarabs do not trigger if the damage is dealt by a token.
Hapatra and Nest of Scarabs do not trigger when token with wither or infect deal combat damage to a creature and die.
I have this output from when I cast Triumph of the Hordes and attack once with a token creature, and once with a nontoken creature. The attackers are blocked and die. Hapatra triggers for the nontoken creature, but not for the token creature. (Flourishing Defenses triggers for both).
The same happens with Nest of Scarabs and wither.
Hapatra, Nest of Scarabs, Corrosive Mentor (gives all your black creatures wither) and a black Insect token on the battlefield. When Corrosive Mentors attacks and is blocked and dies, Hapatra and Nest of Scarabs trigger. They don't trigger for the black Insect token.
The -1/-1 counters are placed each time, but Hapatra and Nest of Scarabs do not trigger if the damage is dealt by a token.