Myles uses Diezel Herbert with Alter Bridge but he uses a Mark IV with Slash. Izzy used III's for a while with the band.
I'd agree with you if were talking strictly the rectifiers but not Mark series, especially the IV. Some more bands where the players use Mesa and Marshall together is Neurosis. Steven Von Till uses a Mark IV as his main rhythm sound, sets the EQ very flat for a dark midrangey tone and is heard just as well as the other guy who used to use JCM 800's in the band, but now he uses dual rectifiers usually. Two very opposite tones that compliment each other well. Another band is Sevendust, one guitarist used a Mark IV for years while the other guy used Marshall's and the dude with the IV's dominated the mix usually. Just check out Woodstock 99 with Sevendust.
I'd agree with you if were talking strictly plexi's because they're such raw, brash amplifiers, and actually very clean compared to a Mesa's gain. Plus they put out about 160 watts in reality so a plexi can bury anything, yes.
When you pull the presence out on a Mark IV you can get a lot more cut out of the amplifier as it makes the upper midrange more present and the treble more clear sounding. It's one of those things I sometimes did when playing with another player who had a Marshall or similar type of amp. By pushing the pull bright on the lead channel it helps clear up the top end as well and makes it very articulate so it really has no problem keeping up with a JCM 800, DSL, TSL or JVM in the cut department, but the best thing to do is just dial a tone that is the complete opposite of a Marshall, more middle mid, lower mid sounding and cut through below the Marshall's upper midrange, there's a big pocket to be heard under those upper midrange frequencies of modern Marshall's cause Mark's are capable of producing much more midrange in those middle mid, lower mid frequencies than modern marshall's are.