Question about "class balance"

I’m curious about what makes a class in OD&D and, by extension, ACKS, “balanced and playable”, if this is even a concern of classes. I’ve only ever really seen arguments occur regarding 3.X material, and they were always phrased in comparison to other PCs rather than the monsters even though PvP is generally not an option. I know that if someone posted a homebrew of a best base attack bonus with sneak attack on the Paizo forums, they’d call it overpowered, yet the assassin in ACKS is pretty much that. Is “class balance” a primary motivator for constructing classes, or are there other goals in mind?

I remember plenty of arguments about class balance in the AD&D 2nd edition days. I can’t really speak to anything before that.

Would those arguments be in about the same vein of “X class is overpowered compared to Y and Z classes”, or did they argue about class balance in a different fashion?

Mostly stuff like you describe (i.e. “fighters are lame compared to rangers” and the like).

I was apart of the 101 session campaign that led/morphed into ACKS, so I can shine some light on the situation.
Despite classes running the gambit from being widely varied to some sharing many features, it felt like everyone could find or carve a niche for themselves with a combination of play style, proficiencies, spells and/or items. So no one class felt like it was completely dominating all the time.
I can’t directly speak to what the precise goals were, but mechanics like cleaving and fighter damage bonus defiantly helped the fighter related classes feel like more than simply damage sponges at higher levels (a complaint often brought up against D&D & kin with regards to fighters vs magic-users).

I think Justin Alexander wrote an excellent essay on class balance:
Using his parlance, ACKS could be described as using a mix of Concept, Naturalistic and Spotlight balance. Naturalistic Balance appears because of the high death rate of low level characters (and characters in general), and the way XP is earned only for surviving adventures and getting back to town with XP. A lot of naturalistic balance is built into the setting assumptions. Spotlight Balance is a result of the fact that different aspects of the game (exploration, diplomacy, combat) favor different character choices.
ACKS also uses what I’d call “longitudinal concept balance” or balance over time. Character classes which are very diverse have high XP requirements and level caps. Such characters advance slower, and are thus less likely to survive past the critical level 1-level 2 thresholds, and they cap out sooner, so they don’t dominate the end game.
We did make some effort to correct some concept imbalance we saw with regard to the general power of fighting-men v. spellcasting, which we think the weapon damage bonus and cleaving has accounted for.

With regard specifically to the assassin, they are definitely a fun and cool character class. I can understand why a 3x/4e player might think they were over-powered. But:

  1. The combination of lighter armor and fewer hit points gives them far less staying power than a comparable fighter. An assassin can wear heavier armor, but then he’s simply a fighter with fewer hit points.
  2. The assassin endgame is a hideout, not a stronghold. This results in a very different character arc over the course of a campaign.

Thanks for the insight. I really appreciate it, and I think it helps me understand the attributes of a class. The hideout instead of a stronghold point really clarifies it.