I'm looking for more cards that support dredge with filling the 'yard early, while being flexible enough as good picks for other decks.
- Castable with -Mana, meaning colorless cards would be sweet too
- Converted mana cost 3 or less
- being able to put 2+ cards in your graveyard
Prime examples I'm already running would be Merfolk Looter or Grapple with the Past.
I'm currently considering adding Mulch and Thought Scour, but unsure if they are useful outside of the dredge deck.
Have you considered simply downsizing your cube somewhat? I'm not sure how many players you have on average, but a cube of that size would have a pretty high variance, which means that it's a lot harder to support neat archetypes. Just a thought! As for cool 6cmc+ cards that would work at your power level, Angel of Serenity has always been a hit, I think.
To provide a bit of a baseline, we'll go down to 3 (very casual) players, and there is still a lot of variance for 3 players at 360.
What we're specifically talking about is the rate that a meta is solved, meaning: how long does it take to figure out how to orient oneself in a format to achieve wins. Once you know how to orient yourself, things can become overly static, restrictive, and stale, as you follow the same general approach to every draft to win.
Cube size really isn't a guard, or ward, against that happening. A lot of WOTC's larger midrange cubes, for example, I would say are guilty of that. There are a lot of potential causes: a wide power band, for instance, can make raw cube size largely symbolic, since a huge portion of it may be obsoleted by the other. Alternatively, perhaps too narrow of a power band, may mean that many cards are overly redundent, or identical in function, to the point where the cube size is again only symbolic, since so many of the cards function interchangably.
Or perhaps worst of all, the proper way to orient yourself in the format might be one dimensional. If planeswalkers, or ETB creatures, or mana rocks, are the clear best thing to do in a format, than players will learn that, and a giant format can start to feel stale and uninteresting very quickly since the way you win is always following the same axis. I think this is what happens to most people.
Thats not to say that cube size can't play a role: essentially, what you are doing by increasing size, is adding raw variables, and a huge density of raw variables can complicate things, and slow down the rate of learning how to properly orient yourself in a format. This can be exciting.
But you can't necessarly industrial complex your way to a never-stale format by jacking up the number of raw variables, since those variables have to also be relevent.
In addition, you have the option of focusing on individual cards that are more dynamic in nature, allowing you to have a small body (consistancy, structure, form) but also a dynamic meta (inconsistancy, open bounds, creativity).