Please read https://letsencrypt.org/2015/10/29/phishing-and-malware.html and The CA's Role in Fighting Phishing and Malware.
You should rather contact fraudulent domain registrar or its hosting provider and report the domain to (for example) Google Safe Browsing. Let’s Encrypt can revoke certificate (but by the matter of policy, they won’t - LE only certifies that your connection to some domain is secure, not that website itself is safe to use), but many browsers do not check revocation status of certificates (I believe that Chrome performs no revocation checks at all, except using CRLSets maintained by Google) - so, certificate revocation will not help.