@Orvillain
I've played a few VH4's and every one of them sounds exactly like you're describing in the OP, and it's specifically the reason I've always been pretty vocal about disliking them.
I have never, ever heard a tight, defined sounding VH4. Every one of them sounds muddy and wooly to me. They all sound like not only is there too much low end being allowed through the preamp, but there's also something going on where they sound like way too many highs are cut out way too early in the preamp as well, like everything above 1k is shunted straight to ground right after the input or something, so you can't even use boosts or EQ's into the front end to gain back that definition even if you wanted it like you can with other muddy amps, because unlike other muddy amps all those highs are lopped away internally either way.
From there, the distortion will add back harmonic content into the upper frequencies and give you plenty of sizzle if you want, but it feels like fake high end to me, like there is zero fundamental signal in the treble frequencies of the guitar itself getting through, just sizzly upper harmonics generated from the low mids and lows being distorted in the preamp.
You probably don't want to hear this, but I don't think there's anything wrong with your amp. Your description matches every other properly functioning VH4 I've played. Your amp sounds exactly like it was designed to sound. Judging by the specific nature of your complaints in the OP, I think you'll be happier in the long run to sell the amp to somebody who really likes VH4's and start looking for something else.
Last thing I'll add is that there is a reason literally every popular guitarist you know about who uses VH4's pairs them with other amps, which I think kind of speaks for itself.
