Many thanks for your suggestion and participation.
enVision supports today Nessus 3.0.6 using cli or NessusClient version 1.0.2 for Vulnerability Assessment (See RSA Secure Care online for more details)
NessusClient 3.x is currently not supported and I assume this is where the request is referring to. We are looking at expanding our support and as soon as Nessus gives us more details we will update.
Many thanks and please keep those questions coming.