Does Taiwanese accent pronounce 他 as hā or am I hearing the end of tā? Watching A Sun (Taiwanese drama, available on Netflix) it sounds to me like the characters are saying 他 as hā. This seems to be true even when people aren't speaking particularly quickly. Am I hearing a regional pronunciation, or is that just the end of tā without the plosive (plosive is the very first part of the T sound where the air stops)?
No, the pronunciation of 他 can be written as ㄊㄚ in Zhuyin. And ㄊ is plosive pronunciation. So the answer is no.