Essentially, the DHS "broke" the game. The old designs were mostly heavily heat-constrained, with the remaining few either carrying limited armament in the first place, giving up armor or speed for heatsinks, or relying on low-heat autocannons. The new advanced "toys" simply gave you more big guns, and the heat dissipation capability to use them continuously. No more "hard choices" between firing that extra weapon this turn and moving more than a couple of hexes next turn, now you can have it all.
The DHS also rendered moot the sole reason for the AC/5: minimal heat buildup.
I see the SCP as a prime candidate for DHS: the ability to fire that big gun and move without building heat every turn, or fire both the main and secondary weapon in the same turn, is more than sufficient justification. My choice for them would be the Jenner: 4ML plus SRM-4 every turn is something you don't just ignore on the battlefield, and when it moves 7/11/5, that's SCARY. As mentioned earlier, when an otherwise basic "Whammy" or "Thud" suddenly starts unloading ALL of their armament at you every turn, rather than exercising "bracket fire" to coax the most out of their prolific weapons batteries and less-than-prolific heatsink sets, that's a HUGE increase in threat level.
It suddenly became a different game with the new heatsinks. The ER and Pulse weaponry had noticable effects (the latter mainly on Light 'Mechs), but even those would have been relatively limited in usefulness due to their higher heat if not for the drastically increased ability to dissipate that heat.
