Dissipation is constant, no matter how many or few weapons you fire.
Since dissipation is constant, you cannot really add together the heat from separate firings and get the same result as if you fired them at once - as you found out. The more heat you generate, the less of an effect you get from the dissipation during the beam duration.
Here's how the math works out:
CLPL is 10 heat over a 1.12 second beam, CERML is 6 heat over a 1.15 second beam.
You run a XL330 with 19 DHS, that's 10 * 2.0 + 9 * 1.4 = 20 + 12.6 = 32.6 / 10 = 3.26 dissipation; fully elited it's 15% more, or 4.14/s dissipation.
Over the course of the CLPL beam, that's 4.14 * 1.12 = 4.6 heat dissipated.
Over the course of the CERML beam, it's 4.14 * 1.15 = 4.7 heat dissipated.
Your heat cap is 30 + 32.6 = 62.6, fully elited it's 20% more, or 75.12.
So firing all those four weapons should put you at
(20 + 12 - 4.7) / 75.12 = 27.3 / 75.12 = 36.3% heat, which corresponds rather well with the 37% you reported.
Firing just the two CLPLs should put you at
(20 - 4.6) / 75.12 = 20.5% heat
and firing just the two CERML should put you at
(12 - 4.7) / 75.12 = 9.7% heat.
Which works out to 30.2% heat, rather close to the 28% you reported.
Edited by stjobe, 05 July 2015 - 02:41 PM.