Typically speaking, yes. The only reason you’d want to hold it is if you’re Rising Mist and know there’s a large amount of damage popping up during that threshold of the bosses HP.
Windwalker is currently the only spec that has chi. Mistweaver has no chi anywhere in the kit, though it is sorely missed.
Our base damage is relatively low. 3+ targets you’d be better off Spinning Crane Kick.
Thunder Focus Tea’s(TFT) optimal combination depends entirely on your playstyle.
Are you more the type to lurk behind the group and heal from afar? (it’s viable but not as strong) If yes, then using it on Renewing Mist would be worthwhile.
That being said, most Mistweavers are playing Rising Mist and the fistweaving playstyle, as it is considerably stronger and far easier on mana consumption. For fistweaving, you always pair it with Rising Sun Kick. You get far more bang for your buck out of extending >all< your HoTs than just 1. So more Rising Sun Kicks via TFT is the only strong option.
Touch of Death also increases are damage to target by X amount (I think it’s 15%) for several seconds. On a boss fight (if fistweaving) you should preHoT everyone with EF and REM so your fistweaving healing is also increased.