I think some of the issues were a result of things going a bit wrong during the pitch/time shift process- the vocal coming out about 30cents detuned from the instrumental. As a result the key changes I made don’t quite work and it sounds discordant. In addition, after mixing I realised that my bass synth was out of tune too.
I’m going to have a tinker, of course you or someone else are quite welcome to put a new vocal to it. :)