The Parthian is designed to be a medium-range harasser. Stick to the edges of the brawl and surprise your opponents with the power of 30 tightly packed LRMs fired at relatively close range, 200-300m is ideal for minimal flight times. 18 DHS mean heat is rarely a problem, whether linked- or chain-firing. Four medium pulse lasers provide a lot of extra punch, and are great for quick pokes while moving in and out of cover.
-1 cMPLas, +1 cTAG +1 cAP and you're set heat wise. You definitely want that TAG as you need to able to counter ECM when having a direct line if sight.
This build already has the active probe, and I've found that in most cases that's enough to punch through ECM at the range this is intended to be fighting at. ECM certainly isn't such a big problem that the loss of firepower from dropping an MPL in favour of TAG is justified in my opinion. If you really want to carry a TAG, I'd do it like this: Since you're not using your missiles to saturate the battlefield from long ranges, but are instead firing them from almost point-blank range along with your lasers, you don't need nearly as many to take down opponents as a dedicated LRMboat would, which means you can afford to take less ammo. I find that in a typical match I only expend about 3,5 tons of ammo anyway, but of course it's always nice to have a little buffer in case of emergencies.
