First of all heres are some imbalances within tech:
1. Archers suck hard, really hard. Maybe give them insane range and damage or an hp buff or something.
2. Ghouls are by far the best tier 1. Compare then to peons. They give less exp, spawn faster, do about the same damage, and have more hp. The only positive about peons is that they have more armor.
3. Peons spawn far too slowly or are far too weak.
4. Huntress, even with their buff, are still bad. One problem is that they spawn much much slower than other tier 2. They take 12 seconds to spawn while fiends take 9 and grunts take 7.5. I suggest reducing the spawn time to around 8 seconds.
5. Raiders aren't a huge improvement over grunts. Raiders have 1 more armor, 200 more hp, the same attack, and faster move speed than grunts.
6. What's the purpose of making infantry and spellbreakers spawn 2 at a time? Why not just double the spawn rate and make them spawn one at a time.
7. Spellbreakers are a little weak defensively. A lot of people tech night elf late game because the human counter (spellbreakers) isn't really viable. Perhaps give them 1 or 2 armor.
8. Archers still suck hard.

Also, I think the key to making tech viable is to buff tech-based heroes, not to buff tech as a whole. For example, farming heroes + tech can easily beat tech heroes + tech when they both have similar techs.

tech needs micro, i.e it's harder to play than just a single hero where you have to click a couple of buttons and basically need mouse only.

I can't play a tech if the rest of the people just go for hero wars since they all gonna cast their aoe in my units.
To sum it up, tech won't be viable except it's that strong that it's imba again.

yah i think the last point is the key one. if you look at the hero killing and AoE skills the numbers are mind boggling. 500 dmg shockwave, 400 dmg FoK with like a four second cool down, pocket factory, etc. With the tech based skills some of them are just trashhhhh (Thorns, Dino's unholy aura, Vigor Aura, Eundurance, Holy Light). They should all be buffed to insane imbal numbers. Holy light should become AoE at higher levels.

Also bring back a defensive tier like the old 3.8 skellies. Like flimsy units that can output a lot of damage really quickly and spawn quickly but give very little gold and exp. They'd suck offensively but be imbal defensively YEAHHHH.

Bring back Spell Immune dryads please. Just give them like 300 hp or something.

I'd rather say, lower elf hp and give them 10/20/30/40/50% resistance to spelldamage.

At human: infantry and spellbreakers spawn 2 at a time to symbolize the philosophy of human: mass units! Human units are basically weaker than their counterparts damage wise, pretty tough on the survivability side and usually come in huge numbers, rendering them suspectible to AoE(even more as their racial makes them pretty though vs physical attacks) yet superior to any other army in a toe to toe battle(as of evasion)
However, I'd like to see a major buff on feedback of knights and tanks, maybe already on breakers... I mean, cmon, tanks deal like 2k damage per hit and burn 4 mana to heroes? wtf?

afair feedback did only burn 1 mana

evasion sucks

spell immunity or resistance to nelf even if they get lower hp on the other hand and nelf will be the only tech played.

if you want spell resistance you will have to pick counter mage. giving a specific tech spell resistance can't lead to anything good...

edit: I can't find the mechanics thread, so I'll post my question here:

does the explosion damage of factorie's goblins get reduced by countermage's aura?

because afaik goblins explosion damage is physical, that's why AoVs get damaged by it for example.

it is mixed damage, similar to the damage of batriders/sappers, thus it gets a) reduced by both spell resistance and armor rating
and b) not blocked by spell immunity