I tried out the deck a little bit. It’s most definitely a solid list, as long as you don’t run into too much Magmar you can make S-rank with it. But your assessment is right. Since this deck relies heavily on cantrips you have to play very efficiently and understand the nuances of most matchups to really take advantage of it. And because it heavily relies on Nimbus, magmar is a difficult matchup.
The deck doesn’t really need more removal. Blood of Air is mostly just a just in case thing. Your primary method of removal should be trading or Falcius, you only need to use Blood of Air when ahead, something really big hits the field, or you really need to deal with a far away minion. And i would adise against Rae, this deck does not need to tubro out Nimbus. It has a strong early game lineup that getting Nimbus out earlier is unnecessary.
As for advice piloting this deck. Lilithe should be a fairly reasonable matchup. She runs very weak early game minions, meaning your minions should over run hers. The trick is dealing with Blood moon and making sure she can’t capitalize on it when it hits the board. Prioritize board over health in these scenarios. Who ever wins the board win the game because you both require set up on the board to win. Hard mulligan for Blood of Air and Skorn. Some good techs for this matchup are Tiger, Superior Mirage, and Star’s Fury.(I’m talking about traditional swarm. Aggro should be an easy matchup. I think I’m the only one who plays Arcanyst. And most of the same things apply to hyper swarm.)
Magmar is a difficult matchup due to Plasma Storm, sticky minions, and Lavaslasher. A big part about playing against Magmar as Vet is learning how to play around Plasma Storm. Plasma Storm is fairly expensive. It eats up Magmar’s turn to cast. With this in mind the best way to deal with it is to make Storm as inefficient as possible. You do this in two ways. A, you have make a board that can survive Plasma Storm. This is why Allomancer is very important in the matchup, it dodges Plasma Storm and doubles as a strong value generator. If you feel you’re board is susceptible to Plasma throw in a Allomancer where Vaath cannot reach. If he Storms you, you’ll have am inion on board and continue pressuring him. B, you learn how not to overcommit. Theoretically, if Plasma wipes your board but you you refill it afterwards it’s a fairly even trade. When you play against Magmar you can’t overcommit to the board. You have to play enough to threaten Magmar but not enough that is you lose it all you’re screwed.
This deck in particular is really susceptible to Magmar since it runs three Nimbus(Nimbus is very susceptible to Transform effects and Plasma Storm which make it very weak to Magmar.). If you seriously struggle with Magmar try adding in some strong neutral minions, namely Thunderhorn or Sunsteel. Or try adding Aymara Healer for some Nimbus.The main trick to the matchup is getting on and sticking on board. Vet’s minions will out value Magmars in a head on matchup, however Magmar excels at stopping you from doing so. Some tips for getting onto the board, try to lead Pax in this matchup. Magmar don’t run dispel because they have so many transform effects. Pax guarantees you get on to the baord and can start contesting Magmar. Try to have 2/3 minions tends to be enough to threaten Magmar, becareful playing more if they’re susceptible to Plasma Storm. I’ve heard that Superior Mirage is a good in the matchup.
Some last thoughts. if you’re having trouble with card draw throw in L’Kian or Sojourner. I’d advise against Spelljammer cause this deck doesn’t like to give your opponent resources. try adding 1-2 copies of Grandmaster Nosh- Rak, it’s a very good finisher in these kind of decks and doubles as strong late game minion. I personally like putting in one copy of Star’s Fury into decks with Fireblaze, it doubles a decent secondary win con.