In tactics games where things try to be balanced, you have a balance of Damage/Range/Durability/Utility
Classes will generally be built like this
+Damage ++Range -Durability –Utility = Archer
+Damage +Range –Durability ++Utility = Mage
++Damage –Range +Durability -Utility = Warrior
So when you get down to it, the balance is pretty shallow unless you decide to go nuts. FF Tactics Advance 2 went fucking nuts, made classes based off of concepts, tested them and then locked them off based on usefulness so you couldn't steamroll the early game.
When you're designing, it's all about making cool shit, then testing to see how well it works and nerfing it if it breaks the game too much or locking it off first behind requirements, if you're going by constrained design you'll suffer for it.
A good example of constrained design that DOES work is Tactics Ogre PSP, each class has a useful role that needs others to cover for them, and so on.
In Tactics ogre, you have four unit types and classes that fit two types at once while having their own gimmicks, and Monster classes which act as certain roles, usually tanks.
You have Warrior, Berserker, Lizardman's Juggernaut and such, which act as tank classes and have little utility, but have passive abilities that stop units from passing their territory without stopping in front of them. this necessitates Archers, which do little but snipe mages and other archers from long distances, but generally struggle against Tank types and Monsters, so your Tanks will mostly be contending with other Tanks.
Then you have Mages, and while they do have magic bolts and such, will hardly do much damage unless they cast the absolute highest level of attack spell, so they're relegated to support and disturbance, being able to accurately and to a terrifying extent completely shut down any type of unit and open them up to a mauling, which is why they're usually targeted first, since they can do this to Dragons, an effective tank unit.
Then you have Clerics, who heal. This is more game changing then you think, since they can give a tank or mage a speed buff to take more turns or just give them more survivability.
And that's not even getting into the Mage Knight classes, who generally do less damage all around, but have unique abilities or affinities that make them exceedingly useful. A Terror Knight can Frighten enemies for example and effectively ruin any defence a Tank type has, or put enemies to sleep or stone like a Mage can, while still having a decent amount of attack, and can also wield Crossbows, which are less effective then bows but can still attack at range, a character like that has no strength, but cannot be blindsided by any type of unit is still useful as hell, especially in a tactics game that is heavily restricted in the amount of damage you can do.
However, because of this, it suffers from very long fights, and it still makes you grind for some godawful reason, both easily fixable in a new game by changing how it's weird class levels work into character levels, or having some sort of catch up mechanic for new classes.
It's not hard to design a tactics game, it's literally all about balance.