Had another thread started with feedback, but in summary: I quite agree with the initial poster. Hellcaller, like Diabolist was for Demonology, seems like a tree designed for Affliction and Destruction was rather bolted on as an afterthought.
Managing a DoT is quite far from the Destruction fantasy of consistent, theoretically fast paced blasts of flame and chaos. Mechanically, the stacking part is rather generic but not inherently bad. However, even from a perspective of tying it into Destruction’s idea of ramping/overwhelming power and Shadowflame, that feels tenuous at absolute best as a thematic tie. Without a total revamp, I’m genuinely not sure how to save it from a Destro perspective – and it does admittedly fit Affliction quite well.