Hi there! I also run a Yidris deck focused more on combat so I have a few ideas that may help based on my own experience.

First off, you have too many big creatures and no real reliable ramp. You need to be able to find lands quick and often and also have some mana rocks to support you too. I do see a few mana rocks but I would look at cards like Darksteel Ingot or Commander's Sphere to boost reliability. You're in green so you have your pick of ramp spells. I prefer Farseek, Skyshroud Claim, and either Cultivate or Kodama's Reach. I would also have a few ramp creatures like Birds of Paradise, Wood Elves, or Solemn Simulacrum.

Okay, now that we have ramped covered, we have to hone in on combat more. You have a few ways to make more combat phases or amplify damage but why not toss in more to boost the chances of getting your combo online?

Hellkite Charger
Savage Ventmaw
Sword of Feast and Famine
Bear Umbra

Want some extra combat phases?

World at War
Seize the Day
Relentless Assault

All of these spells can help you get in even more damage.

Lastly, Yidris is only operating at max when he can be unblockable. You have some solid tools to help with that but two more to consider are:

Thassa, God of the Sea
Rogue's Passage

I would also consider adding some means to manipulate the top of your deck so you have more control of what you're cascading in to. The deck has a lot of awesome pieces so I think you just have to fine tune your strategy and make sure you have the ramp necessary to fuel it.

Cheers!

I didn't catch that you had also asked for individuals to recommend what to cut as well. Here's where I would start:

Song of the Dryads
Imprisoned in the Moon
Berserkers' Onslaught
Bident of Thassa
Scytheclaw
Trailblazer's Boots
Prowler's Helm
Pain Magnification
Familiar Ground
Stolen Identity
Disaster Radius
Calming Verse
Sarkhan Unbroken
Liliana Vess
Jace, Unraveler of Secrets

These are a few cards I think you can cut/replace with cards that provide more support of your theme or provide additional mana fixing and acceleration.

Thanks for the input. Thought I don't understand a few things:

Why remove Liliana Vess? She helps sculpt the top of my library so I can cascade into what I need.

Why remove double-striking Berserkers' Onslaught, unblockable Trailblazer's Boots and free cascade trigger Stolen Identity?

Update: After checking prices (and my wallet) I'm cutting a few very expensive cards that I don't already have. Some recommended cards may have to be cut.

I'm happy to provide some help Jaathik and would be happy to explain my thought process regarding my suggestions for cuts.

When it comes to Liliana Vess, I see her value as a way to help prep for a cascade however, I see her as a 5 CMC one time cascade fixer. Within my meta, Planeswalkers tend to get hate quickly and for 5 mana to use her ability very likely once, I think you could substitute her with a more efficient form of top deck manipulation.

Berserkers' Onslaught is along the same lines in that there are many more mana efficient abilities (many in your deck already) that simply are better. While redundancy isn't a bad thing, I think this slot could be used to much better effect.

Trailblazer's Boots is again a card I feel you already have several effects that produce a similar result more efficiently or in a way that's much harder to deal with so I would recommend opening up that slot for something else.

I see how you're getting a lot of value from the free cascade from Stolen Identity however, that's going to draw a lot of hate to that cipher target quickly. While it's not quite a recurring free cascade, the Expertise cards from Aether Revolt can essentially get you 3 free spells for the cost of one if you have a Yidris trigger.

I agree that liliana vess is not a very good form of reliable deck manipulation. You wanna use something like Sylvan Library or divining top to filter the top of your library. Top is nice cuz your u can do it at instant speed.

There are some creatures that allow you to scry as well. Or you can use the combo I run in my Yidris deck to make infinite mana and get infinite cascade triggers. Pili-Pala + Grand Architect + Etherium-Horn Sorcerer. It's a janky combo but its really fun. You make infinite mana with pili and architect and just bounce and recast the sorcerer to get the triggers.