For several years now I’ve been hearing “ilvl/main stat over secondaries”, however, taking the following list into account:
Restoration Shamans: Crit>Vers
Ele Shaman : Haste>Vers (Windspeaker’s legendary)
Blood DH: Vers>=haste
Havoc and Vengeance: Haste>vers
Guardian Druid: ilvl/vers>haste
Fire Mage: Haste>vers OR mastery
Brewmaster: Vers>crit
Mistweaver: haste>vers (dung) and crit>vers (raid)
Windwalker: vers>mastery
Protection paladin: Haste to 20%, then vers AND/OR mastery (both are good)
Outlaw and Subtlety: vers>crit
Protection warrior: haste>vers
These values come from the WoWhead guides. 14 specs favor versatility as a secondary stat.
There is almost absolutely no incentive for these specs to gear up via Mythic+ except for trinkets, when so few pieces give the desirable stats, if point for point, the pvp gear has more value which are easily found in PvP vendors. The endgame for most players is heroic raiding and so getting to a rating of 1600 is not something out of reach for most players. Pushing to a rating of 1800 requires a bit more team organization, but most casuals should be able to reach that. . The Mythic+ upgrades coming with 9.0.5 end at ilvl 220, which is the same as Rival gear,
If you put a 213 piece with bad secondaries and a 210 piece with BiS secondaries, the above specs will go for the 210. I am a consumate stat-holic and I almost always aim for the perfect pieces to the point of obsession. (That’s not to say I would equip a 210 over a 220, but it is physically and mentally painful to see my bis secondary stats fade away.)
This is one of the reasons why I believe secondary stat reforging should come back as a feature. It’s quite ridiculous that competent PvE players are forced into PvP for maximum sims and ideal stats.