It's struck me that the automatic item level scaling isn't the end of itemization for challenge modes. I've looked around for information but without luck. Here's what I've found:
1. Since ilvl no longer matters (as long as it's 463+), you might as well use the items with the best secondary stats.
2. Scenario reward chests appears to contain loot with a higher total stat budget than other equal ilvl items.
3. Since gems are not scaled, socketed items generally have a higher stat budget than unsocketed ones.
In this case, I'm losing 1 primary stat to gain 39 secondary stats.
As a combat rogue I'd socket Korloff's Raiment with a 320 haste gem, giving me 222 secondary stats at the cost of 20 primary stats - a clear winner.