this for Doomwood rep. Didn't check how good it is so if it isn't good enough for you my apologizes.
To get pyromancer you must first complete the xan saga to access these two quests to use in this merge shop to buy pyromancer. Those quests only require you to kill a boss once however they are DAILY quests meaning you can complete them once per day. So you will have a minimum of 42 days to get pyromancer.
Once you do get pyromancer you only need 1 Class Point to ACCESS the Sigil shop. The two sigils require Rank 10 Doomwood and Embersea like you said