TBH, the problem is that Pyromancy is probably less powerful than a Melta gun at point blank range, and almost certainly less powerful than a Melta Bomb (as they're designed as breaching charges to use to carve through void ship armour).
Also, psycoportation fits better with melee, which having Solar Hero style means is a real strength of his.
Makes sense. Posting on this page for visibility:
[X] Fight the Champions. Each of you face one Champion: Our magic vs Your magic
-[X] Before the battle starts grant wishes to your companions:
--[X] Lorgar Synergy 4 (14 XP); Psychic Vampirism 2 (4 XP)
--[X] Thalassa Psycoportation 4 (14 XP) Psychic Vampirism2 (4 XP)
--[X] Dharock Psycoportation 4 (14 XP) Psychic Vampirism 2 (4 XP)
-[X] Usirian vs Lorgar: Try to use True Faith to exorcise any bound undead it may summon, Steel mind against any fear effect of its scream then Solar Hero Style, try to finish it off with Enuncia
-[X] Sutekh vs Fan: Use EGO-INFUSED PATTERN PRIMACY to ignore its reality warping, MHM to fly and rip it apart. Enuncia as a finisher to render them down to parts
-[X] Ankhaten vs Dharok: Psycoportation to get into position then Solar Hero Style to pound the thing into the ground
-[X] Kharatep vs Thalassa, make herself immune to poison then use a combination of Psycoportation and sheer speed to keep away while she blasts the enemy apart (Action 1: Preternatural Awareness, Action 2: Psycoportation to be as far away from the thing as she can Action 3 Death by a Thousand Cuts to get more actions; Use willpower with Iron Resolve on Preternatural Awareness to take away as many dice as you can for the scene)