I havent done enough to make any assumptions statistically but whenever I started with a 3 affix item with 20-30 FP, and tried to add another affix, it tended to roll on the higher end of the range 10-20 fp and effectively cripples the chances of the item reaching greatness…
by contrast, if I start with something that already has 4 affixes (even if they are relatively low) then the potential to forge something good is much better…
The roll in the range isn’t even distributed, but it’s always biased towards the lower end by the same amount, regardless of what you’re crafting on.
The advantage of starting with 4 affixes over 3 are just that you don’t have to add a fourth affix (which costs 1-20 forging potential if you use a shard).
Exalted items with only 2 affixes are/seem to be penalised as if they are Magic items… Is this how its supposed to be?
Exalted items with 1 or 2 affixes and Exalted items with 3 or 4 affixes are both treated as separate cases from magic and rare items when rolling how much forging potential they start with. Both roll with more forging potential than rares on average. However 1 or 2 affix exalted items do generally start with less forging potential than 3 or 4 affix exalted items.