EDIT: WARNING, firing all 5HML gives you ghost heat as if you are firing 6 HML. ERML sync better with GR than HML but HML is more heat efficient than ERML when it's close, in a prolonged fight. _ Got 1035 damage with this one. 4HML for no ghost heat and higher DPS plus 2xJJ _ Or no JJ for even more DPS _
Just remember that the fifth HML adds an extra 7.2 heat penalty to add to the expected 40 heat if fired together. Still better damage per heat ratio that using ERMLs without ghost heat. 1.059 vs 1.031 https://mwo.smurfy-net.de/equipment#weapon_heatscale
Actually this is a build where you can get away with extra heat. Can't complain if you are putting up good numbers and getting a hero c-bill bonus. If you do get near the heat limit you could chain fire or set up a different group with 4 or less. Like arm mounted lasers.
HML and ERSL kinda match up in range, maybe swapping one HML for two ERSL? The slight loss in alpha could improve the sustained DPS? With Gauss rifles that's often not the most important stat though, as you can fire gauss even at 99% heat, alpha is more important.