Regarding ias: Not sure where you got your numbers from, but from the best info I could find, it looks like much less IAS is needed when using bos.
I'm using info from here: please lmk if it's not accurate:
http://diablo.incgamers.com/forums/showthread.php?t=229326Here It looks like with anything higher than a lvl 9 bos, only 10 IAS is needed to hit the top bp.
A nos coil with do it in other words. This would let you use an extra facet and maras. (Or metalgrid, though that's probably not necessary if you have an infinity merc.)
Or you could do it with a jewel or the ammy.
In any case, if this info is correct, you only need to dedicate 1 slot to IAS if youre using bos.
30ias will get you a 3 frame follow up with fade though. (but a slower initial kick).
I'm thinking I'll just pop another facet in and only gear for more than 10 IAS vs ubers (where I won't be using my headhunter's anyhow.)