I was thinking about the SGII playtest last night (instead of sleeping...), and I realized that we did a couple of things very wrong.
First, foremost, and entirely my fault was small-arms fire resolution. We had been adding up the total firepower and dividing by the armor die type. We were actually supposed to use the range die type. Next time you guys call me on something like that, be more vehement about it (or at the very least, make me look it up again). To be fair, this is in part due to the poor example in the book; their sample target has both a d6 range and a d6 armor, which got me thinking it was armor rather than range. This change has the important implication that even if your d12 range die is rolling like it was a d6, it still protects you by halving your casualties compared to being at a d6 range. This also means that at long range, you're likely to score one, maybe two casualties if you're lucky, rather than the squad-wiping three casualties we kept seeing.
So that was The Big Mistake, which probably made the game significantly more swingy and less fun than it should've been. We also accidentally downgraded our chest-high walls to hedgerows by making them soft cover, our handling of woods was most incorrect (from page 13 - "Units at the edge of woods are in soft cover. Units WITHIN woods may only be engaged by others in the same wood, and then only by close assault, or by artillery."), and our handling of cover in general was quite wrong; cover apparently applies the one or two die shift to both range and armor dice of the target, according to page 14. I had confused this armor die shift with the armor die shift for being In Position, which only applies against attacks from artillery; thus, the effective / casualty-inducing attacks against units in cover (and who wasn't in cover that game?) should have been significantly less deadly.
This last relates to an observation I made last night as well, while reflecting on the complaint that medics were useless. I did some math, and with d6 Armor against weapons with d10 Impact, each casualty has about a .23 probability of being wounded, a .42 probability of being killed outright, and a .35 probability of surviving unharmed. Thus, our choice of gear, namely d6 armored troops armed with d10 impact advanced assault rifles, contributed to the distribution of casualties. We got pretty close to this ratio; there were a total of six kills (two from Glisson's Dwarf Squad and two each from Tim's Orc and Zombie squads), and four wounds (one in Orc Squad, and all three survivors of Zombie Squad (Yes, we were using D&D tokens instead of minis. It was what we had)). Armor d8 being hit with Impact d10 weapons has a .24 probability of wounding, but only a .31 probability of being killed outright, while Armor d10 against Imp d10 weapons has a .2 probability of wounding and a .25 probability of death. Therefore, if we had been applying the cover modifiers to armor, or if we had had better-armored troops to start with, small arms fire would have been significantly less lethal. While armor is still really swingy (it doesn't matter if you have a d12 armor die if you roll a 1), the expected ratio of wounds to kills would have shifted up significantly, making medics much more useful, and the expected ratio of casualties to uninjured effectives would have dropped. So that would've also addressed the complaints of gun combat being either really lethal or totally ineffective by shifting it towards ineffective in the general case...
Finally, there was a caveat in the firing rules that fully effective fire (ie, casualty-inducing fire) also applies a level of suppression to the target. This was bugging me last night too, because it doesn't make a whole lot of sense for fire that causes casualties to be less suppressing than fire that doesn't, so I was glad to find a rule for it in a summary sidebar on page 37. It is annoying that the full-text rules on 36 do not suggest or imply this, though.
I'm sure there's some other stuff we screwed up with morale, but I'll be damned if I know what it was. That might be something to look at after breakfast. Also, with all this stuff in mind, who's up for a rematch?