Druids of the Flame achievement doesn’t work with Fire spells generated by Pyrotechnician.
Druids of the Flame: cast a Fire spell from 10 different classes
Pyrotechnician: after you cast a spell add a random Fire spell to your hand
Tested with Druid and Death Knight. Cast Fire spells generated from Pyrotechnician with both classes. Druids of the Flame achievement counter did not advance.