You probably want griss to do damage if you are already tanky. If we are discussing the most effective way to pair griss, I dont see much point in making her a tank unless you have a caster or rogue as a main character. One reason is because your companions will respawn anyway if their corpse is far enough away from combat. Another reason is as you are melee it is very difficult to have them take damage instead of you (unless you are a rogue). I think warriors can put out alot of aoe damage, so I would give her a two handed weapon and max out her cleave and whirlwind. Fury as well is probably good, I dont remember offhand what she gets for advanced skills. You can probably take down packs of enemies pretty easily if both you and griss do decent aoe damage, but make sure you give yourself trap disarming abilities as griss isnt really able to do that as effectively.
It seems to me that clerics and warriors get the ability to have strength scaling weapons for a reason, mainly because the base damage is higher. Look at the difference between damage of a strength scaling one handed weapon and an agility weapon, there is a big difference in damage. There are certain specialized 1h agility weapons that I would use situationally, but for the most part I would leave agility weapons for the rogues. Agility still scales with 1 handed strength weapons, if you're tanky you should probably still prioritize agility over strength if you are using a shield. The reason for this is because a shield doubles the effectiveness of your armor. But if you arent using a shield I wouldnt worry about armor at all, and I would just try to max out life and mana and use the effectiveness of intervene for defense. The Holy Shield spells and battle prayer and all of that really give the cleric the potential to have the highest armor out of all the classes (meaning you can absorb flat dr from lots of enemies at once.) But if you arent actively building high armor/high resists imo it doesnt seem worth it to me to build around a shield.
Really these are my observations of playing from hard mode. Other players likely have better advice than me, I haven't started an ironman yet.