2004 Cubs had Wood, Prior, Zambrano, Maddux, and Clement. Each of them had posted a 4+ fWAR season in the very recent past. (2002 or 2003). But injuries and time took their toll.
There was also the 2015-16 Mets with Harvey, Matz, deGrom, Syndergaard, and Wheeler. But they had an even tougher time taking the field than the Cubs did.