MTG Salvation

this deck is always going to be clogged with 4+-drops

I disagree. I think you can do well with 6/7 4-drops, which will always be smoother than 8. Even though you wanna go up to 8 cards, they won't be 4 identical legendary creatures, or things that you can't flicker for some sort of value, as it is the case for the 4 Vannifars (and some of its pieces). My point is that 4 Van + 4 Cat is the clunkiest 4-drop package of all time, and I don't trust it on paper.

Vannifar and Felidar not having much synergy in this deck can hurt a bit, but I'm not quite convinced that going midrange is the way to go when we can combo off so fast and so consistently

I didn't mean to go midrange. If you want to be even more combo-ish with Felidar, you can play early drops that go infinite, like Auriok Champion, Anafenza, Kin-Tree Spirit or Champion of Lambholt, but it seems nobody plays that configuration, so...
If you take Vannifar on the other hand, you want more early drops to curve nicely and have something to sacrifice. What if your board is Vannifar + Felidar ? How do you combo off ? Here's another way to make Vannifar quite useless if you don't have a Zealous Conscripts to untap her, for example.

I'd rather have 4 Vans along with 1 Resto, Shalai and Elenda for a total 7 4-drops, and make sure I have enough 2/3-drops to assemble and recur the combo chain, which is one of your concerns by the way. But it's criticism that I make while I haven't tested your list posted above, so I will in order to sharpen my pov.

Copycat isn't Tier 1 because the combo unfortunately relies on a PW, like other comboes rely on enchantments (these are the 2 least supported card types to dig and tutor). If Twin worked, it's because, instead of searching for the combo pieces, you controled the game and comboed off when possible. That's what Jeskai Copycat tries to do nowadays.

Green decks, however, need to dig or tutor for the combo pieces. In a format where Stirrings digs for 5 to find a land or an artifact, here we have a deck that don't want to run noncreature spells, and the best at that for PWs is Oath of Nissa that digs for only 3.

Unfortunately there isn't a combo yet that's really bolt proof right? Unless I missed something.

Don't worry this is not very important. I believe Lectrys's focus is more important than whether the combo can succeed through a bolt :

how often it can Hail Mary a win despite getting the combo disrupted, just by comboing off again

@Lectrys,
what I'm the most worried about is the lack of synergy between 4 Vans and 4 Cats. When your opening hand is a bunch of 4-drops (8 is quite the load !), you mulligan with a tear in the eye. The Cat can't blink Van for value, multiple Vans can't co-exist... as close as they look, the mix of 2 different archetypes might be a huge trap. Isn't it more important to have a nice curve ready to welcome Cat blinks and Saheeli's clones ?

I feel like Vannifar only lacks slightly better chain pieces, but I hope I'm wrong, or I hope Wizards will accidentally print cards for the archetype very soon !

Given how fast the format is, I'd say that counting on something else than the combo to win is delusional. Birthing Pod was able to do that because it was one turn faster, you could search for your bullet pretty fast. Nowadays the best option for that kind of play is Eldritch Evolution. In all fairness, Pod lost most of G1s to very fast openings from decks like Ascendancy Combo, Burn, Affinity, Tron... So don't expect Vannifar to do as good or better while she's one turn slower. If by any magic we're still alive on turn 4/5, we must combo off, because it's too late for silver bullets to save the day.

So cards like Knight of Autumn are not even a given in the deck. It's a debatable card in GW Value Town, Vizier Company and so on because it's truly a SB card and doesn't help win as many G1s as people wish.

I'm not entirely sure about playing Voice of Resurgence: I've always loved that card, and it sure sinergizes well with Vannifar and Evolution, but is it worth playing or it could give some space to other useful things?

Another good example. Back in the day it fought Jund, Abzan, Twin, nowadays where is it good ? Wall of Omens, Coiling Oracle might be cards to consider.

I actually played Pod in Modern recently to figure out whether Shaheen Soorani was out of his mind or not about Pod being unbannable. Well, believe me or not, I struggled real hard against the Tier 1 decks (while I was a dedicated Pod player back in the day). Kiki Pod is closer to Vannifar because both decks focus on the combo, while Thune Pod rather is the Value Town. My point is the meta is so hostile to midrange decks, that playing Vannifar in a midrange shell is no good. It has to be a combo shell in my humble opinion.

@Kathal, well said, we agree overall.

Rhythm isn't a dedicated combo card, but makes all played creatures better while the other two cards are purely combo cards. Hence, not being able to find it via tutors is not that big of an problem in this case. You can compare it to a PW basically, on what it does.

We then agree the card is cute, it makes "creatures better" like an anthem would, but we don't play anthems in these kinds of decks, and we never have in Modern. Anthems effects only go along with a synergistic feature : tribes or tokens.

Rhythm of the Wild will be better if it's part of a combo (+ Murderous Redcap + Viscera Seer = infinite damage, for example) or if there's a strong synergy (Hardened Scales ?). Enchantment-based combo decks are garbage because we can't tutor all the pieces. Knight Bantfall is another good example of a miss (Amulet Titan can Ancient Stirrings for Amulet on the other hand, you know, artifacts are much better supported in all formats). Those decks suck so much that even in a combo shell, they don't work ! So playing Rhythm for value only - and mostly for Vannifar - seems completely out of the realm of competitiveness.

Now compared to a PW, well I'd play Saheeli + Felidar everyday over Rhythm + Vannifar, because the first is a combo kill while the second is only a ramp effect. I mean, Saheeli gives haste too, and Vannifar is considered in Copycat decks... That being said, Copycat doesn't warp the format at all because PWs are as crappy to tutor as enchantments.

It may be iffy to compare enchantments because they serve different purposes, but truth is no matter what you use them for, they're all clunky in most decks, especially the more they cost. You may argue Hardened Scales, Spreading Seas, Bitterblossom and Intangible Virtue don't hurt deckbulding, and to me it's thanks to the low mana investment on top of a global synergy in the archetype.

Is Magus of the Moon viable with this complex manabase? I really love this card, but a couple of times it caused some trouble with my own lands. I'm still pretty unsure if it's the case to move him to the sideboard or not.

I'd say Magus is a meta call, and now is not the time for the card to shine. Many Arclight Phoenix decks, Dredge which wants to cast Conflagrate against creature decks anyway, and so on. Magus belongs in the SB for Tron.
Second reason is that this card is cute in a deck that wants to combo every game in the current meta. Cut the cute.

I really like Rhythm of the Wild, but adding 3 other non-creature spells could be a problem. I guess the only card we can remove with this perspective in mind is Eldritch Evolution, but, as I said before, I'm pretty interested on seeing if it can be good toghether with Chord.

Enchantments are real bad in combo decks that can't find them consistently. I realized it the hard way with Intruder Alarm, a broken card in a format that don't support enchantment combos. People are so desperate they play Drift of Phantasms, what a joke ! Even Jeskai Ascendancy doesn't do anything in the format, while it was the most broken deck during the Treasure Cruise Era. Once again, cut the cute.

The main problem I see is the combo chain itself makes you play cute cards already, so you guys better not add more.