This is definitely the right approach.
However, all this does is make a mono-earth deck highly dependent on 1) Pillars and 2) Earth Elementals.
I think a better approach to improving mono decks is to give them 3 or 4 new cards which work well together, within the element.
A purely hypothetical example here would be:
Gnome Gemfinder: Creature 1/2 - Cost:
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Ability: Each Turn
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is generated.
Mountain Fortress:
Permanent - Cost:
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Ability: At the end of every turn, all your creatures gain +0/+N. Where N is your total Earth Quanta divided by 10.
Landslide: Permanent - Cost:
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Ability: Deal N damage damage to all non-earth creatures in play, where N is your total number of Earth Pillars divided by 2. Lose 2 Earth Pillars every time you play this effect. [/list]
Another, again, purely hypothetical example for a mono improvement for Air this time (air needs it lets be honest.
Storm Spirit: Creature N/2 (N/4 Upgraded) - Cost:
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Ability: N is the number of Wind Pillars divided by 2.
Storm Generator: Permanent - Cost:
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Ability: Storm Clouds: Cost
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: Create 2 Wind Pillars until the end of your turn. Can be used more than once per turn.
Tesla Coil: Permanent - Cost:
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Ability: Static Release: Cost:
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: Create either 1 Storm Spirit or cast Thunderstorm[/list]
I think little easy to understand batches of 3 to 5 cards (bit like Booster packs? in other CCGs?) are an easy way to promote synergies
within an element./Just my thoughts.