There's always discussions around "overvalued" and "overpowered" units. Some unit are looked at as "insane" etc.

But in the end I get the feeling it's more about how to find the right "countermeasures" to deal with a particular unit.
Some units are probably "overpowered" vs some enemies/units and the other way around.
First of all though, I agree that if in NetEpic Gold using the original floater/flier rules, than it actually is a bit overpowered

We use fliers/floaters but also the optional rules in Gold, and we have also added the Palladium rule that the add 25cm extra for being on high altitude, goes both ways.
That balances it quite well.
I always play squats and my opponent Orks and in a game we played the other day, we actually had a discussion around the Overlords, and "overpowered" or not, thinking of its price, its features and compared it to other Ork units (in this case). So interesting I stumbled upon this old thread:)
We played a 4K game and I had two Overlords and he had picked three Stompa mobs. My opponent thought the Overlord was a bit overpowered, and I didn't think it's that much better than a Stompa mob (if better at all) which has the same price (250 in Gold).
I know you can't really black and white compare two units like that, but it can give an indication at least. The reason we compared those is they cost the same, they are both sort of super heavies where they get an "extra" save.
I would save the Overlord is superior vs units being infantry to vehicles and the stompas from more vehicles/heavy vehicles and up.
Anyway, what we discussed was that the Overlord has one 6d6 5+ (-2TSM) weapon and a 4d6 5+ (0) weapon. The Stompa mob a 3d6 3+ (-4) weapon. That could sound like the OVerlord is way better with it's ten dices, but not really. Statistically they will both make two hits on the more powerful weapon, but the Stompa mob weapon is much more powerful with it's -4 TSM, so a bit advantage to the stompas.
Then the Overlord has those extra 4d6 that statistically gives it 1-2 more hits with a 0 modifier. I would say comparing them they are now quite well balanced. The Overlord would be better versus weaker save units and the Stompas better versus heavier vehicles.
Now the OVerlord has that melta bomb, but during my 25 years of playing epic, I have NEVER had the chance to use it. Not sure I play it correctly, but it just never comes into play

Then we have the CAF where the STompas dominate with it's three Stompas with +8 caf and the Overlord is alone and only has +5. Advantage Stompas.
Then we have the movement, 5cm more for the Overlord, so advantage Overlord.
And then there's this extra save, when the Stompas are hit, they completely survive on a 1, get damaged and has a -1 to hit modifier on 2-3 and is destroyed on 4-6. The Overlord survives on 1-3 and gets an extra armour save throw on 4-5, so advantage Overlord. BUT, there's just one OVerlord so even though it's gets a better second save, if it fails, its gone, finito.
Then we have some Floater advantages for the OVerlord, it gets this extra -1 shoot the thin part TSM modifier. It can't get pinned and maybe something else I forgot.
I would though say, they are pretty equal compared, if we talk balance. And no, you can't compare units black and white just like this, but my point is, they are well balanced, you just need to use the Overlord where it does its business bust and the same with the Stompas.
Lets just say I had no idea how effective a couple of Shokk attakk guns could be versus my floater. My opponent picked a couple of those and made life really difficult with my floaters (they have LoS, so if a floater is high up, it ALWAYS sees it). Is that unbalanced? No, it's just that the Shokk Attak guns work really well against fliers and I have to come up with a countermeasure

Since this post isn't long enough, let me add that we setup a fun little fight, the OVerlord vs a Stompa Mob (remember now, alternate rules, so the Stompas could fire on my Overlord). My friend was sure the Overlord would dominate and I was quite sure of the opposite. We played ten fights of just first fire against each other and switched who started every turn.
Let's just say a Stompa mob completely slaughters the Overlord in a face to face combat between those two.
It was 9-1 to the Stompa Mob.
Unbalanced? No, its probably just not a good idea for an Overlord to go up against Stompas.
Again, sorry for long post, but I think this is quite interesting
