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You're not the first person to suggest having mass trap cards.

Storm Wizards get Windstorm. This spell places a 20% trap on all enemies. You can boost this spell by combining it with a potent trap spell (adds 10%).

To fix this; create two different trap cards:

• Mass trap card
• Enhancer card that lets you upgrade any single trap card into a group trap card
  

Fuel is a fantastic single target spell that places 3 traps on the same target:

Fire http://www.wizard101central.com/wiki/Spell:Fuel

Life http://www.wizard101central.com/wiki/Spell:Life_Fuel

Myth http://www.wizard101central.com/wiki/Spell:Mythic_Fuel
***this is a pet talent called Mythic Fuel ***

What the OP is referring to, is a spell that casts traps on all enemies; instead of just a single target.

Currently, only the storm school has such a spell, and its called Windstorm:

Storm http://www.wizard101central.com/wiki/Spell:Windstorm

Another work around solution for the OP is for KI to create a spell card that converts a single trap target card, into a mass trap target card.