Two problems come to mind. One easy, one hard.
The easy problem is that while pairing together might generally be stronger than solo play, pairing together might not confer the same ELO benefit in all ELO ranges. For example, premades are a recognizable power at top ELO (you can see who they are, since the population is smaller, and good premades can carry REALLY hard). However, at lower ELO, game knowledge and coordination are lower, and even if you coordinate, if you can't hit the broadside of a barn, it matters little. Disclaimer: these numbers (and all that follow on ELO) are pulled out of my Rear Center Torso. The effect might actually be the opposite direction in practice - I'm just providing an example of the fact that the impact of grouping might not be universally the same.
So, the answer might be to (based on empirical information you have access to that we don't), derive the ELO boost that a group gives, not as a universal constant, but as a function of player ELO. E.g. Grouped_4_ELO = 50 + (Base_ELO*1.1). It doesn't even need to follow a determined function - you could use smoothing/interpolation to follow an arbitrary empirically derived pattern.
The hard problem is to account for systematic differences in group play. Some groups may be very coordinated and able to significantly outperform their theoretical ELO rating, because their teamplay is quite good. Others might not even be on comms. The average-by-ELO method described above might not capture this. At the same time, until there is a lot of data on a player in this regard, it is doesn't make sense to treat him as far from average.
Therefore it might make sense to treat players as an average (as above) until they have ~100 premade games and as many pure PUG under their belt, then compare their performance in PUG relatative to group, and use that to form a differential modifier for group play for each individual. E.G. Player X has played 100 PUG and 100 4 mans. His ELO currently is 1000. Up until this point, his ELO modifier for group matches was +150 - the default value for 1000 ELO. He played all "fair" matches with ~50% win expectancy, and won 50% of his PUG matches, and 60% of groups. His ELO now gets a +100 adjustment, whenever he is grouped.
Regarding the SHS/DHS tonnage/crit tradeoff:
The traditional argument for SHS being relevant is that they consume fewer crit slots than DHS, therefore making them balanced. While this seem plausible on the surface, it is a fallacy.
Why? EHS - Effective Heat Sinks - the total level of cooling is totally skewed in DHS favor. If you run SHS, your EHS = your SHS. If you run DHS, your EHS = 2.0xEngine DHS + 1.4xOtherDHS.
If you take DHS and at least a 250-rated engine (basically all 'Mechs use an engine this large, or larger), and NO heat sinks, you have already saved 10 crit slots compared to SHS cooling the same quantity (same EHS for 10 in-engine doubles and 20 singles). Excluding engine slots, it takes carrying nearly 30 (I have a table for the exact numbers of crits saved) SHS before you're saving ANY crit slots compared to an eqivalently cooled DHS 'Mech (and you're paying upwards of 12 tons for those one or two slots!). The bigger the engine gets, the higher the tradeoff point.
Since you get so much for free out of engine DHS, SHS need to do something better than them to be balanced. Like heat threshold.
Edited by Peter2000, 12 April 2014 - 02:05 PM.