Photobucket is banned because some people have and will continue to put stolen art up on photobucket.
On to the card itself.
3 devourers are more valuable than 1 3|5 creature. Hence the enemy will never pop the carrier.
Since the enemy will never kill the carrier you would have to supply the death (cremation possibly).
As such the carrier should be priced with the means of destruction in mind.
I personally would value the cheapest destruction (cremation) as +1 card in effective cost.
3 devourers in one card are worth 6
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+ 3 cards.
So the carrier is worth 6
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+2 cards.
This is about the equivalent of 8
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+ 1card.
But what if the carrier is not used as such?
It would have a modest protection from destructive CC (excluding replacement CC like Skull Shield or Alfatoxin) this is probably worth 1
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.
So the actual Slug should be worth 7
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+ 1 card.
7|1-5, 6|6-7, 5|8-9 and 4|10+ are all stats that would be worth 7
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+1card
In summary change:
Casting Cost to: 8
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|7
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Attack to: 7|7
HP to: 5|5