Maybe, depending on how you define overrated. Overpriced, sure. My favorite marks are definitely now the iic's (no +) now that I've experienced 2 examples. More raw, jagged, aggressive voicing than +'s (guys please no more + upgrades lol), but they still don't have that same feel, liquidity or lead tones like the +'s. I'm not sure if they have the same type of note density either. I'd have to AB
All I know is I've AB'ed several IIC+'s in the past with plenty of examples of mark iii's, iv's. a V, JP2C and Mark 7 and I felt it was clearly a level (or 2 in some cases) above those amps when compared, mostly in detail going on around the notes and feel (I think that perceived feel is the byproduct of that extra detail or complexity in tone). They wouldn't quite make my personal top 5 favorite high gain amps I've played for my taste, but definitely to me exceptional amps that are up there that offer qualities none of the other marks do IME
Like any of these sought after versions (like a Rev C or Blueface also) I'm guessing enough guys appreciated the differences that caused a big premium for them. No, they don't imo sound 3-5x better or x dollars better than the next best alternatives like a mark iv, iii, rev f, g as examples, but it is what it is. If we're not putting money into the equation, those versions are special (to me just plain better). If you wanna factor in cost, they don't sound nearly as much better as the price difference could suggest to some, but almost always the case with this stuff
I totally agree about the reverb/delay part. Really not a fan of that, especially if the goal is to be an amp demo of all things