It looks like you went for a more ally-centric approach, which is interesting to me because I do enjoy tribal/thematic builds but I wouldn't have expected to see
Sea Gate Loremaster simply due to summoning sickness and high MV. I wonder about
Hagra Diabolist or
Kalastria Healer over the loremaster as an ally-centric "wincon" (arguing the loremaster is more wincon that card advantage). The inclusion of
Intruder Alarm makes sense in the current build, but I suspect that
Jeskai Ascendancy provides similar effects and better card selection without potentially enabling your opponents. I do enjoy the
Retraction Helix line with it though, which the ascendancy does not enable.
I am somewhat skeptical of
Halimar Excavator as a wincon due to the number of things which milling out either enables (opposing labman/eldrazi titan/
Endurance). Honestly, I think
Young Pyromancer is one of the best Zada support cards, so if the intention is a low curve creature that would be my swap. Alternatively, if you intended this as a self-mill strategy then some more recursion may be warranted. I didn't see much beyond
Mavinda, Students' Advocate.
On both of the above; I will note that if you intend to stay on the Allies backup plan:
Urza's Incubator pulls serious weight on 3+ MV tribal decks. This would almost certainly be better than
Thought Vessel if you retain this part of the build. It pays for itself off Tazri+Zada alone, and nearly lets you drop both on the next turn on curve.
I'm also somewhat skeptical of
Mavinda, Students' Advocate due to the once/turn limitation. Is the intention to set up over the course of a turn cycle with a cantrip or two on each turn? I'm having a bit of difficulty envisioning a state where Mavinda would outperform something like
Underworld Breach for mana efficiency, and the threat profile that would make Mavinda good (3+ creatures with Zada) is nearly kill on sight anyway, so delaying over turns doesn't really fly under the radar. Can you explain the inclusion? Even something like
Archaeomancer would potentially have more combo potential while being a creature if the MV can be supported.
If you do include Mavinda with the intention to build over turns, then I'd drop as many sorcery speed cantrips as possible. I think your list currently has 5, likely for color or MV reasons. I found several instant speed options which may work better for a draw-over-time approach.
Bandage,
Defiant Strike,
Twisted Image, or even
Fleeting Distraction would give you more options for card sequencing at the cost of less valuable effects than the evasion provided by
Ancestral Anger,
Cloak of Feathers,
Nighthaze or
Slip Through Space.
Renegade Tactics would probably be the swap before those. The other feature of instant speed cantrips is the "go off in response" option, which is very potent in more control oriented games.
I'm also not entirely sure about the purpose of
Harmonic Prodigy. It doesn't have that many creatures that meet it's criteria and it doesn't have a combo that I see with it. It seems like an available deck slot.
I really like
Startle as a version of
Spawning Breath that also draws cards. That's absurd and I should look into adding that to my blue+Zada list.
I think counting the proactive protection pieces you're around 11 cards of disruption, which is about average, I think. As the deck is proactive, this is reasonable but I'd worry if you sit down against three fast cEDH decks that you might not be disruptive enough. You're in a similar deck space to my only fringe cEDH (
Unesh, Criosphinx Sovereign) where you don't really start threatening a win in most cases until you've invested 6+ mana on the battlefield. Honestly, I swear by
Mana Drain as a semi-ritual that's also disruption and I think it would outperform
Thought Vessel as "ramp". I know it helps me land a 6 drop commander in turns 2-4 so it should help ramp Tazri into Zada.
My last comment on your current list is the relatively few was to interact with a
Rule of Law effect. These are not uncommon in stax or semi-stax lists and I know from experience that those are very painful. If you can't counter it then you're either drawing on each turn or waiting until you can kill the player controlling it.
Force of Vigor or some other removal seems potent here.