If you are using LastPass without 2FA (YubiKey, etc), people attacking LastPass itself is really the least of your problems. I'd be much more concerned about keyloggers grabbing your password. BeEF can pop up a LastPass phishing prompt if you just happen to load the wrong javascript file.
Using just one string of characters to protect ALL of your passwords is insane.
Using just one string of characters to protect ALL of your passwords is insane.