I have always used ranged units as garrisons simply for the extra ranged attack they provide.
Since the 'garrisons take damage' mechanic was introduced I have begun to re-examine my strategy.
Personally I don't like that garrisons take damage, and therefore weak ranged units even more so.
For what its worth I agree with the OP that ranged units are a poor choice based on the state of the mod now. Apparently though I'm in the minority in thinking garrisons taking damage is a bad idea.
Garrisons taking damage in my opinion was one of the best changes this mod ever done, and ranged units are okay garrisons as long as no melee unit is attacking the city, they are useful as a counter against an archer attack, since they don't take as much damage from the shoots while garrisoned and can attack at the same range, but against melee attackers a solid melee unit can almost double the life of the city, the only loss of the new system is that you can no longer save those 1hp surviving units by hiding them inside a city.