What makes a stat "interesting"

[Khalithar]

That being said, it's not like people are going to toss out an upgrade just it's not the BiS (due to secondary stats). An alleged upgrade can be rather disappointing, weight-wise, if non-optimal, but especially when the primary stat weight gains are as strong per ilvl increase as they are in XIV, there are no truly wasted pieces upon acquisition unless you already have equal or higher tier gear compared to the place you're looting.

Actually, this is EXACTLY the case and was one of the rampant problems the devs had with raiders back in WoW, players would actually not want an upgrade unless it was BiS. I can't find the exact quote as it's pretty old, but it's one of the mentalities Blizzard found really problematic with raiders. That could very easily happen here as well.

[Shurrikhan]

Actually, this is EXACTLY the case and was one of the rampant problems the devs had with raiders back in WoW, players would actually not want an upgrade unless it was BiS. I can't find the exact quote as it's pretty old, but it's one of the mentalities Blizzard found really problematic with raiders. That could very easily happen here as well.

Sorry, I meant specifically in XIV.

In WoW: WoD, level-cap gearing with secondary stats increasing damage by about .8x. In other words, about 40% of your damage was due to secondary stats. By the end, secondary stats had increased damage by about 3.5x. In other words, they tremendously outweighed the value of XIV's secondary. Compare that to FFXIV's secondary stat values, where I have a weight of 323.2 from my combined secondary stats (almost entirely crit, SS second) on my Bard relative to a 1216 weight of primary attack stat. Even including its contributed Bloodletter procs, it's probably making up not much more than a third of my damage. It was that majority of a late-game WoD player's gear-damage contribution. Part of that is because secondary stats would enhance relevant properties more per point than ours — whereas tier ilvl jumps are rather similar, including into Mythic/Savage — and part of that was because of especially advantageous class mechanics (similar to Bloodletter). The closest analog we have to that is BLM's taking off at the end of ARR due to higher secondary stat weights. Blizzard has also released posts, though one of the most concretely aimed somehow sunk into the unmentioned, saying their looking to curtail exactly that. Legion itself has aimed to provide more core gameplay early on, and quickly taper off secondary stat contribution in order to better linearize their worth against upgrades by primary stat, (so that, say, an ilvl bonus is still to some degree the way to go until about a tier higher than in WoD).

Our (FFXIV's) actual primary/secondary stat balance is still leagues different that WoW's, while WoW seems to be taking steps to move in our direction.