It might be counter intuitive but really, I've learned to pay more attention to the primary (and sometimes the first secondary) stat increase.
I've got a crit chance up mod that adds 17 speed (I think it's a 2dot) which is pretty nice.
It seems like speed, potency, and +crit damage primary stats give you the most bang for your buck.
Protection is good too and I like +health for tanks and healers.
There are probably speed set mods that also have speed as a primary stat increase but frankly I don't have the resources to farm for them.