As far as the HPPC's D/T ratio goes, well it's better than the ISPPC. 1.5 for the HPPC, 1.43 for the PPC. It's D/H is also sliiiightly better, due to the random 0.5 heat missing from it, and its D/C is definitely better at 3.75 vs 3.33.
It also beats the IS ERPPC in every category except range. Honestly, the HPPC is the best PPC the IS has even if that's something like getting first in the special olympics.
Though the LPPC would be able to match it if its GH limit was 6 or something like that (ie so that they both did 30 damage at a time). Then the situation would be that the LPPC wins on tonnage, but the HPPC wins on crits+hardpoints, so it depends on what your bottleneck is.
Clearly though what the IS needs is... PPC Capacitors.
Anyway though, I'm just not sure:
TDR-5SS
Definitely pretty on the toasty side. Nice alpha for an IS mech I guess, but the medium lasers have extremely poor range synergy and I just don't know what to do about them. Ditch them for heat sinks? Replace them for a LL or a pair of LPPCs? Just consider them backup weapons? Replace them with ERMLs and run even hotter?
Also up in the air: if I ditch the AMS I can squeeze ooooone more DHS in there. But it seems like an AMS can earn its weight back so consistently if there is even one LRM/ATM/MRM user on the field. With all the new missile weapons its target profile sure has expanded, and it only needs to prevent 32 damage to be worth 1t of armor, a rather low bar to clear. On the other hand... missile weapons in general are still kind of underpowered so maybe I shouldn't care about them?
There's also options that aren't quite cemented with the engine: a sturdy STD250 would put me at -1 heat sink and +16 armor (due to a half-ton gap), but then this mech has no CT or head weapons so it's not like I care about dying after a double-ST loss. A fragile XL300 on the other hand could get me +1 heatsink and an extra ton that I don't really have enough crit space to spend. And I can't bump it to a 305 because that'd need 1.5 tons. Moar AMS ammo? I'm leaning toward its current Light 280 as the best compromise, honestly.