I think, regardless of whether or not Juggernauts are altered/balanced or not, that Lord Xia hit the nail on the head as far as the need to balance the races are concerned.
Before proposing my suggestions for how to change/improve the races, let us go ahead and write out what the final two races do (playable, but not attached to any of the pre-made leaders):
MANCER gain +1 accuracy per level. While I suppose this can add stability to higher level units, it is arguably worse than the Wraith racial (keyword arguably) in that it has minimal to no impact for most of the game (or all of it, depending on your playstyle).
URXEN gain +2 attack when in an army of 5 or larger. Would have been amazing if Urxens, rather than Quenar, had slaves, but is still a nice mid-to-late game bonus, and can be rushed early if you really want to pack an early punch. Not game breaking, and it could be argued that by the time it comes online it is negligible, but it is a free damage bonus, and especially nice if a majority of the army is Urxen.
With that out of the way, these are some proposals I have to help make all the races feel powerful and unique. These ideas are primarily to spark discussion, so feel free to dislike my ideas, or propose better ones (you will anyway, right?).
Let us say Trogs don't change (I don't like Beserk, but that is neither here nor there):
I wouldn't change Men either, but instead focusing on improving the AI use of henchmen.
Golems could get an inherit bonus that says they get a damage reduction percentage equal to the damage they would otherwise take. For example, if the Golem would be hit for 50 damage, it would get a 50% reduction modifier, reducing the damage to 25. The reduction modifier could cap out at 90%, to prevent 100 damage attacks from doing zero damage. This would lead to having to balance having no armor (improving your chance for higher modifiers, but making you more susceptible to weaker units) or lots of armor (negating weak units in a typical fashion, while weakening effectiveness against stronger units). an alternate ratio (1: 1.33 1:1.5 1:2 [damage:reduction]) can also be used if 1:1 seems too small (can obviously go the other way if too large). This may not be the best idea, but it is the best I've come up with so far.
I also wouldn't change Quenar (slaves are really powerful [odd thing to say about inherently weak beings]), but suggest that the AI get more slave unlocks naturally so that the human doesn't have to play them a couple of times before they can reach their full potential.
I honestly like the Krax ability (Fortify). If the aforementioned bug exists, fix it. Teach the AI how to use Fortify properly. Perhaps gains the ability to build units that have any of the other races blood abilities, like fire-resistant Quenar dragon hunters, Tarthan scouts and weak/medium monster hunters, etc. (fellow traitors). I know that sounds very weak (it does to me, any way), but I honestly don't know what to do as far as a Krax unit.
I honestly like the Tarth ability in theory. In practice, not so much, but the theory is cool (reverse Urxen in a way). I'd love to see a unit that compliments this (maybe something that can hit every square on the battlefield simultaneously with friendly fire, but doesn't harm itself). Then again, Tarth needs a lot of work in general (come on, just remove the stealth ability from the game. Let them remain mobile guerillas)...
Amarians are a lawful people who think they, by right, should rule (and, in my mind, by extension: control). What I think they could use is a special unit class that can start with controlling combat abilities (like Stun), especially if they can be done from range, applied to magic attacks, and/or cannot be resisted.
Wraiths, being bound to Ceresa in the Resoln description, gives me the idea that their special units, being bound to the sovereign, don't die unless he/she/it does. Upon being killed, they return to the capital exactly like the sovereign. To avoid an unbeatable capital, they could start at one life when reanimated, and be unable to move until they're healed to full (rather than an arbitrary amount of turns). In addition, they can only heal 1 HP per turn, regardless of other modifiers. This would both benefit their low HP (having them recover faster), keep high level units from being too powerful in their pseudo-immortality, and add some merit to their +3 HP on kill if they're down to their capital and the stakes are high.
Mancers, being a trading, merchant race, could have access to special mercenary units. They can only be rush or bought with gold or influence, but in return could have more perks slots than normal, unique perks, or have their perks be free.
It is a shame slaves are already taken, and Urxens can't have that mechanic. As people who, when performing acts in large numbers (and with migratory tendencies) have changed history, they might benefit from some sort of leader type unit who either can have followers bonded to his army for bonuses (bonuses dependent on the leader built), or makes his own followers. For example, I make my leader so every unit bonded to him heals X HP per turn, where X is the units level. Either units can bond to him in exchange for the inability to leave that stack, or he creates his own, bonded units whether with gold, mana, or influence (perhaps getting different types of units from each?).
Like I said, just my suggestions, and some of them I don't even think are good. Hoping to breed a different line of balance discussion in hopes of a better game for everyone.