Drone Guidance Systems: Probably better as a Drone Upgrade than an armywide special rule. Infringing on Blood Angels here.
Dynamic Entry: How can I not like this

?
Precise Maneuvers: This is very ambiguous and poorly worded. If your intent was to have it be something similar to the Positional Relay, just use the Positional Relay's wording.
Regulated Thrust: Sure why not.
Tactical Shift: Very fancy!
Tau Commander: Unnecessary: Just make the units with Tau Commander be a 1+ slot (I'm assuming they're the Shas'
El and Shas'O)
Tau Auxiliaries: Any army can already take allies under 2000 points.
Untainted by the Warp: Fluff might be off a bit - it's not the amount of taint, it's their presence entirely.
Overall: There's a lot of special rules here. I'd say, after the auxiliaries, choose the 3 you feel best suit. You can apply more specific rules, like Regulated Thrust, to the units that use them.
Tau Commander: Either describe the special rule in the
HQ slot, or at the beginning. It doesn't need to be in both sections (See directly above).
Wargear note for Commanders: You're misreading splitfire. ONLY ONE MODEL from the unit gets to splitfire. Also, XV-3 suit mentions Reliable Thrust, which I'm assuming was changed to Regulated Thrust.
Drone mention: The wording on this is ambiguous and poor. "Can join other units as normal" for an independent character
STILL MEANS HE WOULD HAVE TO LEAVE THE DRONES.
Combat Link: Really needs some heavy rules-intensive revision. I have no clue what this thing does outside of a vague 'feeling'.
Celestial Wrath: Reword the scatter clause. Use a similar weapon for reference.
Double Dealings: Doesn't state that they no longer arrive on 3+. Now enemy units arrive on 5+ AND 3+. Ammending this to "instead of normal" would fix.
Death Oath: Makes his death penalty/benefit sort of useless. That's all. Is also really expensive.
Ethereal Guardians: They don't have targeting arrays. They have target arrays.
Crisis Suits: W3 for no points increase? In fact, a points DECREASE? These are now worth it just to load em up with free burst cannons or cheap fusion guns and go nuts, even assaulting with them! D: Also, again what's with all the splitfire - it doesn't do what I think you think it does. Also, why does every other character for normal squadrons cost 10, while the shas'vre is only a 5 point bump? Regardless, these things will take out 2-3 marines each in close combat.
A quick note on markerlights: You've given Fire Warriors the ability to kill anything in the game. Sniper + S5 Pulse Rifle = for 2 markerlight tokens, you get BS4 firewarriors with S5 snipers. Wat. It gets better, battle link 4 firewarrior units together - the shasuis can take markerlights for 5 points, and with the current wordings, can all fire their markerlights at one unit, and then 1 firewarrior team fires at that unit while the others gain its benefits against all the other units they decide to fire at - meaning you have 4 teams of (11 firing) bs4 S5 snipers firing at 4 different units from 30" away for a mere 482 points. And they're all scoring and ignore night fighting.
definitely advocating a rework on Markerlight effects and their interaction with Command link or whatever it is.
I'll get to the rest later, good work so far but you might want to reconsider how you've costed a few things. It's best to start with overcosted and chisel down, than to go at it undercosted and bulk up.