Without the information of where you are picking up the orbs, I can't give you a specific reason why you're not finding an orb with Tier2 Staffmods (FNova).
If you want to investigate further, search for "
Staffmods". Near the end of the "Affix Selection" section of the linked page, you'll find a good writeup for staffmods. In HU, the skill tiers are: Tier1=lvl1, Tier2=lvl6, Tier3=lvl12, Tier4=lvl20, Tier5=lvl28, Tier6=lvl36. As implied on that page, if you're searching for orbs with ilvl greater than 37, then you'll never find one with +FNova. Consider searching orbs dropped around A1 or A2 Norm. It should be impossible to find an Orb with +FNova and +CMastery together, since those skills are 4 Tiers apart. Similarly, +Teeth with +BSpirit shouldn't be possible to find on wands or NecroHeads. This is related to the difficulty of finding a nice +3Prayer Warscepter (by the time warscepters drop, they can almost no longer spawn with +Tier1 skills).
