My guess is that they don't want story spoilers; having the main story autopsied in great detail before release would probably hurt sales more than any testing would have helped - not because the story isn't expected to be good, but because "I already know what will happen" takes away something from those that purchase on or after release.I fully agree that balancing such a mechanic is very tough (especially when people are gonna try and abuse it;-)). I just don't think they have to make it a 'goal' until they get some statistics in from us. When they release the game they are going to get such massive data in from Pilot kills in PvE/PvP that they can decide to tweak the %'s. I'd rather they get the game out and patch it up the following weeks than meticulously trying to maximize everything just to patch it a few days later when the real data trickles in. That is one of the reasons why companies release their game under BETA conditions so the game is tested on player abuse + lesser issues with patching.
Look, this game is gonna get patched either way to include stuff that fell out (we all understand that), but I am amazed that HBS isn't getting insurance on player complaints by going BETA + getting some serious data from the massive fan-base (I doubt any company can hire 20.000+ testers) that they can work with before they do a 'full' launch.
As for testing, HBS have had both internal and external testers playing through the game for a while now - Kiva even mentions that the latest ramp-up in MechWarrior injury rate is done because testers were playing through the game without (m)any MechWarrior fatalities.
They also extensively use simulation - unless I misremember Kiva has previously said she ran "hundreds" of AI-on-AI battles per day to get statistics on everything from hit rates to pilot injuries - only to tweak some numbers and run it again to see what effect that had. This has been going on for some months now.
They have a set rate of MechWarrior injury/fatality in mind that they think makes the game interesting enough, with the right mix of risk and reward; the game will release with the best balance HBS can muster in all areas, including this one. Whether that is good enough for everyone is of course debatable, but please remember that their livelihood depends on this - they have very good motivation to release the best game they can.