teas can release astringent flavors and bitter oils which can (relatively) ruin your brew, so they need to be steeped at lower temps for a little longer and never brought above 150 - 155 degrees. In general, you use hot water for tea you are going to drink hot, and cold or room temp brew tea you are going to drink cold.
Regardless, tea does not behave like hops. No matter when you add it, it will add flavor and aroma (relative to the amount you use.) tea will steep at any temp, however the lower the temp the longer the steeping time. I say cold brew and steep it at room temp for 2 weeks in the secondary. This way you get all the flavor and aroma and none of the nasty bitters.