Suppose a ciphertext $c$ was encrypted from plaintext $m$, and we know something about the form of $m$; say, for example, that $m$ is English text. We can attempt to brute-force $m$ from $c$ by computing $E^{-1}(c)$ for all possible encryption functions $E$ and discarding the values of $E^{-1}(c)$ which are not English text. However, the probability of $E^{-1}(c)$ consisting entirely of English text (assuming $E$ behaves ''randomly'') decreases as a function of the block size. Hence, it seems that a larger block size results in fewer false positives.
Am I correct in saying that large block sizes are more susceptible to this kind of attack? Do we have to keep this in mind when designing encryption techniques, or are other factors (e.g. key length) more likely to be security bottlenecks?