To be honest, the problem with heatsinks isn't dissipation.
It's heat storage. You see, the weapons entire balance structure is based on a set amount of heat being a maximum. That amount is 40. Or at least, it should be.
The devs implemented heatsinks in a way so that each normal heatsink in your mech adds 1 point to your mechs capacity (set to 30 in game, since 10 heatsinks are required, this does set a minimum of 40 storage when using single heatsinks).
However, additional heatsinks increase this capacity. For single heatsinks, this may be fair enough, however double heatsinks can store 2 heat for every engine DHS, and 1.4 heat for every additional one outside this. This matters because MWO is a real time game. More capacity = more time to shoot before you're forced to face the consequences of a heat imbalanced build. Heatsink boating is the name of the game as it drastically increases just how much stupidity you can get away with.
To give you an example - my stalker has 21 DHS total, 10 in engine, 11 in mech (1 stored in an extra engine slot as it has a 275 in it). This gives me 65.4 + xp efficiencies in heat capacity - and double heatsink cooling. You read that right - I can store 1.75x the normal amount of heat than the weapons are balanced for. This is why you see 6xPPC stalkers at all, and 6xSRM cats firing near constantly. DHS dissipation + DHS heat storage = too much heat efficiency.
What to do about it? Well, if they're dead set on heat storage going up with # of heatsinks, reduce DHS storage to SHS levels. Ideally, I would recommend hardcapping at 40 - aka; just get rid of it as it's an unnecessary mechanic.
Edited by Monky, 15 March 2013 - 08:55 PM.