If it was just another cover band doing Metallica I’d say that’s pretty good, a full tribute band though I think should sound closer than that, at least get a mesa 5 band and scoop some mids
If I was these guys I would get a Synergy IIC module, pop it in the loop of the Marshall. Use all of the Marshall for KEA and RTL and turn on the loop for later stuff.
Wrong tone for the wrong genre though. I mean the playing is great but the high mids and lack of thundering lows sounds kinda weird for Metallica songs. At least run a V EQ in the loop to scoop things a little bit?