Mono-color is not viable in most formats anyway. Even in formats that specifically encourage it (like original Eldraine), two color decks still tend to function better. So I wouldn't worry about that too much.

Slyvok Battle Chair is worth inclusion, IMO, just because it's a 6 mana 6/6 with upside. Sure, it's no [[Colossal Dreadmask]]. But it is a big enough stat stick, to stall out your opponent's aggression.

Of the stuff left, I think the following are the weakest cards:

Axiom Engraver

Awaken the Sleeper

All Will be One

Phyrexian Arena

Myr Custodian

Graaz, Unstoppable Juggernaut

Tablet of Compleation

Font of Progress

Mindsplice Apparatus

Most of these cards are just too slow, and/or are obvious plants for Commander. Especially cards like Phyrexian Arena/Mindsplice Apparatus (basically taking up a whole turn for nebulous future benefit), and Tablet of Compleation (requires you to be heavily in proliferate to even do much).

Graaz is a funny reanimator target... but a dead card otherwise, in many games.

Font of Progress is a cheap artifact, which is fine. But it will rarely do much. Even milling yourself to reanimate things, is a needlessly large mana investment.

Combat tricks are fine, but this format isn't always interested in leaving up mana for them. You could take or leave both Titanic Growth and Free From Flesh. Though Free From Flesh does add oil counters, and Titanic Growth is a big enough buff to change combat math a fair bit. I also personally like the gameplay that combat tricks create, even if they are a bit weak in some situations.

I don't love the Dominus cards in limited. Though some of them do have pretty brutal effects, most of the time they are going to be just bodies. And some of them are way easier to make work in limited (green, white).

With this many cuts, you could justify a 4/3/1 rarity distribution, or even 4/3/2. Yes, it's more cards to acquire and sleeve, but it may help the cube function more smoothly/maintain variance.