well from what I have also been reading the usual balance issues in Warhammer games is about, that is, Chaos tend to be able to run straight into combat and then become impervious. Maybe there should be a design philosophy for Warhammer computer games by now because it seems to be the usual issues that developers do not always grasp between army designs and how these will affect implementation
I agree though it is not easy to envision how balance comes about in a fps game with substantially different forces requiring different tactics (and to some extent skill levels), e.g. Eldar are going to be overspecialised, which is all the more reason to choose classes that can take on multiple roles for the sake of group tactics
I've also heard Eldar are coming next and may be released shortly, which sounds good, but anticipating ping and lag issues by playing overseas (250+ ping) means choosing ranged units firstly, apparently Eldar will have quite a few basic starting classes
Let's see... Currently the main three classes (a la the 'riflemen,' the heavy weapons, and 'melee jump assault') of the Space Marines and the Chaos Marines are identical, including weapon choice. Instead of having stupid point differentials in like tabletop lol.
They have added 2 classes to these main 3: One is a Support character, the other is a Ground Melee. Those have different mechanics between the two, though the intents behind the mechanics are similar:
Going in respective order of SM and Chaos, we've got Apothecaries and Sorcerers as Support. They are the ones that can heal others without needing a medpac. In the game there is a "downed/wounded state" if you get mowed down, and then you have to be shot at again (or executed) to be completely dead. You can crawl around if just wounded lol. During this wounded state, any type of unit can spend about 3 seconds "rescuing" you (though you rez at critical health, so you do have to find healing). Instead, a Apothecary or Sorcerer can rescue you VERY fast... I believe Apoths can do it by a melee smack with healing tool, and Sorcerers can rescue you from a distance at a quick rate, both all the way to full health. Sorcerers also have some additional spells, I forget what - and they are still adding/removing/tweaking these, and I don't remember what else an Apothecary does lol. But in general, you can consider them support. And neither have ranged weapons (though Sorcs may be able to do some mild damage from afar).
For Ground Melee, SM gets guys with Storm Shields, and Chaos Marines have guys with Marks of Nurgle. Both of course are melee only, no ranged weapons. The Storm Shield is very strong, I'm not sure how much damage it negates but I think it makes anything non-energy negligible. It's also interesting.. primarily it's an "active" ability, as in you have to press the button to hold it in front of you (and then you walk slowly). But it has the passive benefit of blocking from the left side when they're running, as they're wielded on their left arm, whereas their right arm is open.
Chaos Mark of Nurgle guys simply have a huge health pool. (Though without a "regenerating shield" mechanic) But it's enough health that they're quite tanky.
So basically Ground Melee = tanky. I don't believe either one has strong armor. But in any case, I believe the intent is to have both be equally survivable and be equally maneuverable (or equally NOT maneuverable).
---
Now, you do pose a good point because they still have the ability to add Khorne Berserkers, Noise Marines, Rubric Marines, and shit. I have no idea if they will because I don't pay attention much lol. But so far they aren't trying to differentiate the races in their base classes as they would in a strategy game, if you know what I mean.
Interestingly enough, it may be
Eldar that could cause balance issues with specialized units that can are much better at melee (Banshees, Scorpions) than the others. Because Marines are still quite generalists. On the other hand, the developers may simply not adhere to fluff
that much and still keep the base 3 classes (riflemen, heavy weapons, and specialized assault) closer in mechanics, and about equally balanced in strength. Then if going by precedent they'd add the specialized units after those three (Warlocks and Fire Dragons? Warp Spiders? Striking Scorpions? Sadly I don't think they plan on adding all the specialist units..).
Though, the assault troops with Eldar don't quite match the Marines at all... Their jump troops are ranged units/bombers IIRC (Swooping Hawks), whereas their fast assault are fast ground units like Howling Banshees. So perhaps they will have to make those different.
But I think 'riflemen'/'Tactical' equivalents should be okay by using Dire Avengers, and then use Dark Reapers as heavy support.
Would be cool to see Harlequins though!
---
Also there are still gonna be more vehicles, like speeders, buggies, bikes, etc. And I have no idea how that will balance out. Actually the current maps are too small for them to be that useful.