Hey
@benjameenbear, I overall like the list. There are a few things that stand out to me however.
Faeburrow Elder - Great card, I personally run it in my not as high power lists. Tapping for 5 man is pretty strong! However, how often will you have all 5 color's of permanents in play? In my experience it will tap for 3-4 mana most times, and thats still strong, but it would be really awkward if you need that 1 color you can't produce. It does have vigilance allowing it to work well with Najeela however; it is still 3 mana for a mana dork. And you have Ad Naus in the deck....Not sold on this decision.
Ad Nauseam - Love this card. Wonderful card advantage, however just a quick glance over your list, its pretty high on the CMC side from what I'm seeing. Granted I haven't done the math, but if you take an average of 25 life from Ad Naus, with 3-4 cmc cards you're looking at probably 11 Cards, with 3 of those being lands (roughly 1/3). I think if you could drop the average CMC of the deck, definitely include this, however in your current build, I would be scared to cast this.
Arcane Signet - I'll be honest, I used to run this in my deck and I was criticized as it was "too slow". I never thought it was, until the game where it was. It happened multiple games where playing the Signet was just a feels bad play/turn. I guess this is meta dependent and depends on where you want the overall decklist to be at power wise. Personally would cut this, but it does its job.
Notion Thief - cries in Hullbreacher banning.....
Esper Sentinel - Surprised you aren't running this. Personally, I'm finding it difficult to decide what to cut anymore from my list, but looking at your list, I would put this over a variety of cards. Play testing puts it over
Ponder at the very least, so I would definitely consider this inclusion.
Ancient Tomb - Honestly not a fan in a Najeela list. You want to make colors, not colorless. Even a basic Forest is better in my opinion. Pongo has the mana base pretty figured out for the Primer version, and I believe he cover's why ancient tomb isn't there. Sure it helps cast Najeela, but you will most times be casting her T2 anyway, so Tomb doesn't really speed that up (except for the rare occasion of a lotus/tomb opening).
As far as your counterspell package, I think its solid but do agree it's a little much.
Counterspell or
Spell Queller would be my cuts. I've already talked about the queller, I don't think it has a home in cEDH, but potentially high power where you can allow for some pet cards/decisions. Counterspell being double blue and NOT providing the mana advantage that Mana Drain does is a feels bad. Holding up double blue can hurt a lot especially since that would be majorly telegraphed (less so if you hold up 4+ mana/lands but if thats the case, why haven't you won :p).
On to
Nature's Will. Pongo goes into this extensively about why it is ran over Druid's Repository in the primer, and I recommend you to read it. However; I can also speak a little bit on it. So Nature's Will, while you do need the correct colors, can win with as little as 3 lands and Najeela on the field with it. If you can make all 5 color's with your 3 lands, and have 2 open to attack opponents, you win. You attack with Najeela targeting P1, the token comes in attacking P2. Assuming both connect, you have 2 Nature's Will activations, allowing you to make all 5 color's. On the flip side you must be attacking with 5 creatures (or a combination of creatures/lands that allow you to make 5 mana) in order for Druid's Repository to work. The major downside of the repository is that it doesn't work on the tokens coming into play. So while it is a mana cost less, it is most times, slower than Nature's Will. Also you have the down side of losing all that mana if the repository is destroyed. Having used both (and most cards that combo with Najeela) I would actually use the
Sword of Feast and Famine over the repository if you are going that route. This at least protects Najeela, and makes her beefier and easier to connect with players.
Hope this helps some. Really it all comes down to if you want this to be high power or cEDH. High power, the list is absolutely fine. Personally I think there are a few weak spots in regards to cEDH.