well first of all you can;t get a block every 30 seconds because they aren't even introduced into the block chain that often. It's one every 60 seconds.
the 2nd thing to be aware of is this - as long as the pool has at least 10% of the network hash (as a basic rule of thumb) that pool is going to get 10% of the block - in this case 6 blocks out of 60.
just because you're in a larger pool than may be finding more blocks does not mean you're going to get more coins. It doesn't work that way.
it's real simple: this coin has a block time of 60 seconds and the reward is 100 coins per block so therefore on a daily basis this coins generates 60 (blocks per hours) X 100 (coins per block) X 24 (hours) = 144,000 coins and those coins get divided among everyone mining the coin.
therefore is you're in a pool that of find 50% (Pool A) of the blocks that pool is going to get 72,000 coins
if you're in a pool that's finding 25% (Pool B) of the blocks that pool is going to get 36,000 coins
now here is where the math gets good : let's assume that the network hash between all the pool is 1,000 MH/s or 1 GH/s
and you have 100 mh/s
the bottom line is that you're going to get 10% of the coins which = 14,400
so back to the pools:
Using 1,000 Mh/s network hash as the example:
Pool A has 500 MH/s
Pool B has 250 MH/s
and you have 100 MH/s
So - if you mine in Pool A then you're going to get 20% of their daily reward which we already calculated at 72,000 coin and your 20% is : 14,400
If you're mining in Pool B then you're going to get 40% of their daily reward which is (36,000 coins * .4 ) = 14,400
Either way you're going to wind up with the same number of coins.
The only caveat is that if you have a really small percentage of network hash (perhaps 1 or 2 percent of less) you probably don;t want to be in a pool all by yourself just form the frustration factor of having to wait forever to find a block all by yourself.
The bottom line is that you're going to get the same number of coins regardless of where you mine as long as YOU have a decent percentage of network hash (I tell people 5% as a general rule of thumb) and remember this - if you're mining to make $$$ and you find a great coin to mine - keep your mouth shut and don't get online telling everyone - let other's figure it out for themselves - because everyone else who joins in DILUTES you're ability to mine that coin. - THAT'S JUST THE WAY IT WORKS.
I hope this has been helpful.