Sarna.net states:
"Pulse lasers differ from traditional laser weaponry, in that instead of firing one powerful beam, they maintain several laser beams fired off in quick succession. While offering an overall increased rate of fire, the heat output also increases accordingly. Pulse lasers increase damage because they allow vaporized armor to dissipate from the location of damage. This allows subsequent pulses to reach the target area without being diffused by the vapor."
Anyway from technical perspective, it makes no sense... multiple weaker pulses would not produce more heat.. they would produce less, because you are not using peak power... Only explanation to this is that these rules were written in 80ties by somebody with just basic physics knowledge, yet in this case, its terribly wrong.. Even if you actually used peek power for pulses, their limited time would automatically mean weapon would overheat a lot less than weapon that would use same amount of power but with one constant beam...
Anyway, Sarna.net stats for Medium Pulse Laser are 6DMG and 4Heat, which translates to 30Dmg and 12Heat (5xDmg 3xHeat).. so yeah, current weapons have way too much heat..