I do not think the OP fully comprehends what the 40% heat sink efficiency reduction means for many clan builds. First we must review certain mechanics that you claim make clan mechs superior. The first one I would want to address is your 60% damage reduction for hitting a side torso that is destroyed. You only receive the 60% reduction if the destroyed arm mount is hit and not the side torso. For example a Shadowcat's destroyed arm mount is decently large compared to the side torso so you can expect some hits to receive the 60% damage reduction, while a Mad Dog's destroyed arm mount is so small compared to the mass of the side torso that it would rarely receive that 60% damage reduction.
The efficiency of shielding with damaged arms or side torso's is a function of mech design and hit boxes and is not an exclusive defense of one faction or the other. Generally humanoid mechs with flat front profiles and large arms can shield better with their damaged components than other types of mechs, regardless if they are Clan or Inner Sphere.
Next, the Clan will notice the increase heat sink efficiency reduction with damage XL engines. Let us use for an Example the trial Shadow Cat Prime(c) variant. This build has it's weapons mounted to the right so the pilot can use the left side to shield. This variant is running 13 heat sinks, 3 external, and the ten internal that come standard with the clan XL 270 engine. During battle the Shadow Cat pilot successfully uses their left side to shield and loses the left torso. Before the patch the mech effectively lost four heat sinks. The 2 external in the left side and the 20% reduction for their internal heat sinks effectively knocking out 2 more. Post Patch the Shadow Cat is losing 6 heat sinks nearly half of it's cooling effectiveness.
Notating the delay on the paper doll to register destroy components, the pilot could easily fire their weapons as or just after the side torso is destroyed which in the heat of most battles would result in a shutdown for a significant time period. Assuming this does not result in destruction from enemy fire, the excessive heat causes heat damage to the internals. This heat damage could result in destruction of the CT, or other side torso, if they are heavily damage, or could destroy a heavily damaged component such as a leg. Assuming this creeping heat damage did not destroy the mech, the greatly reduced cooling ability has massively reduced the Shadow Cat's ability to fight with it's armament. Now the Shadow Cat pilot can mitigate this risk some what. Relocating the heat sinks in the left torso to the right arm will off set that some what. However their are several Meta laser vomit builds that this is not an option, and this especially effects Clan builds that use asymmetrical builds to shield.
Another example would be the Hell Bringer Clan ER Medium Laser vomit build. In this design the Clan pilot uses the right side of the mech to shield with 6 Clan ER Med Lasers in the rest of the mech. Typically this build has a total of 20 heat sinks and is going to have 3 external heat sinks in the right arm, and 5 in the right torso, with 13 heat sinks in the engine. Prior to the patch, destruction of the right torso would result in the loss of 10.6 heat sinks, the ones located in the right side components and 2.6 from the internal engine from the 20% heat reduction. Post patch the mech will now lose 13.2 heat sinks, well over half of it's cooling capability. Note it has not lost any weapons but the firepower is now greatly reduced because the pilot cannot fire all of his weapons without overheating, their ability to alpha being completely removed. The Hell Bringer suffers all the problems of the Shadow cat in the above example, but more so, as it as lost even more of it's cooling capability and has no way to mitigate the increased heat penalty. Add to this that Clan weapons tend to run hotter than IS weapons and the issue is compounded.
This heat penalty is a creeping doom added to the Clan XL engine. Where an IS XL engine, when destroyed, simply takes out the mech, the Clan XL now adds the frustration of a slow death whether from the death in shutdown, the slow destruction to heat damage, or being crippled despite having the majority of their weapons intact. Point is, the Clans will notice the greater heat penalty, and pilots of omni mechs cannot opt out of this new feature as they cannot change their engines to STD.
Edited by Rusharn, 25 January 2017 - 02:55 PM.