Its better than what Im getting (-32601 Method run_cmdline not supported.) 
Are you on windows? CLI access isn't available on Windows. It may work over RPC.
Im guessing one word seeds arent very secure then . 11 bits of entropy for a word? Im guessing thats to prevent underflow?
. 11 bits of entropy for a word? Im guessing thats to prevent underflow? It's 11 because the default dictionary is 2048 words (2^11). If you use a larger dictionary you can encode more bits. You can replace the default dictionaries with your own if you like. Here's one with nearly 9k words. It's a combination of the electrum dictionary and one I downloaded from the EFF's site. On linux you can replace the Electrum dictionary in /lib/python3/site-packages/ele colctrum/wordlist directory.
Ah thats quite cool. I think I have every word in the Collins English dictionary somewhere so thatll be interesting to try...
Is electrum happy to go over 256 bits of entropy?
Just to note, be careful backuping this new dictionary file if you intend to use that new wallet and seed. If in future you'd need to reinstall or upgrade Electrum, and recreate the wallet (with your seed), then you'd need also the same file to generate your wallet addresses and keys. So you'd be dependant not only of your seed, but also of this file.