Comparing with a Seared Melter that burns at 1000 degrees:
This seems to not be a visual bug since I cannot melt certain blocks that have high melting temps.
Forge - 2575
MC: 1.12.2
Tcomplement: 0.2.2b
TCon: 2.8.1.49
Ceramics: 1.3.3b
Let me know if you need any more information :)
Darkosto