The actual XKCD password generator suggests using padding as well. Using non-alphabet padding symbols (even if they are all the same and as trivial as 111 or !

The actual XKCD password generator suggests using padding as well. Using non-alphabet padding symbols (even if they are all the same and as trivial as 111 or !!! at both ends) will improve entropy by a decent amount while being just as easy to remember. However the password itself is still only 1 aspect of security. There are many cases where there are far easier attack vectors that don't including cracking hashes.