How much leaf do you use?
I tend to make tea in either 12 or 16 ounce cups. I usually use a well rounded teaspoon for each mug, and then a little extra for no particular reason. It’s definitely not an exact science. When I brew tea for iced tea, I usually fill half of a three inch tea ball for a little bit less than 2 quart container.
For iced tea I use like 3x the amount I use for a single mug, usually about 3 perfect pot spoonfuls. Often I end up re steeping leaves in a small amount of water & add it to the cold tea to bring up more flavour.
As you said OP, this is a somewhat subjective question. I tend to adhere to the directions of the company selling the tea which is usually at a teaspoon for a cup or so. If it is to be used for iced tea, I like to double it. However, I will sometimes add more to get a stronger taste and that is where that experimentation comes in. I also will tend to add a little more leaf if I know the tea has been sitting for several months. Of course, I will also steep a little longer in this situation too. However, I don’t like to go over a 2 teaspoons as I feel if you are doing that, the issue is with the quality of the tea. The tea should stand on its own and if it requires more than that to make a good cup, I would rather switch to another company’s variety that is stronger and cheaper.
For single powerful infusions i use 1.25-1.5g per 100ml(ca 3oz), whites and greens 2g.
Less would work aswell but would need longer infusiontimes.
For multiple infusions twice that.
For Gong fu brewing 5-7g / 100ml