I have a really hard time imagining that a modern pitch list which runs only 5-6 removals for Leyline is just fine but if you make most of those removal uncounterable at the cost of being slower a portion of the time, that this is a horribly losing proposition.
Like, compared to that list mine (several posts above) is lacking Hollow One and Dread Return, but packs a bit more disruption and has a very comparable anti-hate package that usually can't be countered. I can see how that would be similar, I can see how mine might be slightly worse, or I can see how mine would be way better. I really don't think mine could be way worse though, because it's the same core strategy with a very similar deck post-board.
Is it possible that Mark's deck was bad for reasons other than the Cavern of Souls package? When you're playing a faster build of Dredge it hurts a lot to run into any hate because your opponent got to operate with little or no disruption and you have to use those speed elements to catch up once you've cleared the path. With more disruption you're not necessarily behind in the first place
Mark's list was fairly stock, at the time, outside of the sideboard if I remember correctly (that is to say it was some variant of Always Sunny Dredge). This was all prior to you and I developing the transformational board though since I recall I was playing a very early iteration of my creature transformations (aka bad BUG fish). So it was quite a few years ago. Its possible that the meta has shifted to make this more playable, but seems unlikely to me as the format was super slow comparatively, which is why my plan, at the time, of Dryad Arbors + casting stuff like Golgari Thugs could get there in game 2/3s.
I wonder if it would be worth running a random UB elemental to tutor up as a pitch card. I think that's just going too deep, but part of me wants to make Muldrotha, the Gravetide Vintage "playable"
At least it's a reasonably 'okay' Dread Return target as well, if not encumbered by Leyline. Play Bazaar every turn is a little like Sunny.
Muldrotha is definitely playable, but not really in these lists. There is a really nice infinite loop with it, lotus and animate dead that allows you to recur all your non-land permanents
What is this loop? I'm aware of the loop to Animate Dead a Phantasmal Image with Lotus (LED for cEDH) but not this.
2xAnimate Dead / Dance of the Dead
1xLotus (or LED)
Generate infinite mana using loop, you can cast any creatures/planeswalkers during this period as well. Next, cast Muldrothas directly using the infinite mana and you can cast any artifacts/enchantments.