Played 5 games this year with squats using your thurgrimms stronghold list against Eldar and Codex Marines. Played 2000 and then 3000 point battles as the army grew. Felt balanced enough against these oponents but initially I was always pressed against my table edge by these very fast and agressive armies until I started combining layered defences with mobile flanking formations. The lack of scouts really does hurt this army but not so much that they feel unbalanced, you just have to learn to play defence another way.
Here's my feedback about the units:
Autonomon - Makes Robot s a bit tougher but never really impressed me. Ok.
Spotter - I like the new version of the spotter rule. The 45 designator range on the Iron Hawk is ok. The wording is simple to avoid confusion and it promotes movement of the slow WE giving the impression of a big rolling monster firing it's guns as it advances rather than a high armour artillery piece. Also consistant with SM-era Squat WE.
The older rule was ok but this one works much better with the army.
The 10 cm movement never really had much impact on the games I played but I guess keeping things simple (without infiltrator on Bersekers) is better. 15 cm, 10 cm, meh...
Warriors - Better now with the missile launcher. I think they are fine with 1/2 heavy weapon per stand as long as the price keeps low. They are the workshorse of this list. You need plenty of these and cheap. The Rapier and Thunderers upgrades are just right both in points cost and stats.
Bersekers - Felt rather fragile formations. Used them for counterattacks against vulnerable formations. Even with support they always get mauled after a single assault because of their armour making them useless after that. Still, very cheap. The Rhinos are a must for these.
Spartan's/Rhinos - I like keeping things simple, so a Rhino always worked for me since the SM2 days. That being said, I have used them very sparingly (only in one formation per army) just because I think lighter transport vehicles should keep being somewhat restricted for squats. If you need to get around get a proper vehicle like a Leviathan

Hearthguard - Their role at beefing up the brotherhood is very well reflected with the inspiring and leader abilites. Their stats don't need to be great for this. Ok right now.
Mole Mortar - Reducing their BP's seems fine for me. A small mortar formation shouldn't have a greater impact than a Colossus in the game.
Thudd Gun - Like Mole Mortar, small cheap formation for harassing with good range.
Robots - I like them, their stats make them tough opponents. The autonomon rules also makes them tougher, to a small degree.
Iron Eagle/Hawk - These I really liked! Fast, great range, the armor and pop-up makes them hard. The price is high but seems fair for all this. 2 Formations backed-up with 2 Overlord make up for a very tough flanking force. Keep out the AA from these. Unnecessary and overcomplicated.
Overlord - At 225 I'd still use them. But it is hard to put a points value on these. What's really overboard with these is their bomb load but the 15cm range and the support craft rule makes it very dangerous to really use them. They always felt very vulnerable but almost always survived the battle. Both because I usually place them on flanks and because my gaming group has a metagame that makes WE and TK weapons rarelly used, You're right, Moscovian, these are very tricky...
Leviathan and Colossus - Both are great WE. The Void shields and armor are adequate making them very tough. They both carry the Doomsday cannon that deserves it's name. The placement of this gun affects everything your enemy does
from placement to where he assaults and what objectives he'll try to take The Leviathan really felt like a cheap way to get an extra doomsday cannon in play to me. Upping the cost to 375 helps this. I have very limited experience with WE so I am hesitating to say that 375 and 450 still fells like a low points cost for these for their impact. But again, I play in a WE-limited environment.
Great job so far! Congratulations to all the team!