Largely this is due to to the fact that a somewhat balanced list is defined as much by what it could do as what it can't do. By opening it up to unlimited allied lists you basically can build counter balances for one from the other to mask the inbuilt weaknesses. Basically you get the mess of unbound armies from our larger scaled brethren.
Now for beer and pretzels, it's great!

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He's a lawyer and a super-villian. That's like having a shark with a bazooka!
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I HAVE NO POINT-
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