When do I abandon set bonuses for higher I-level? (Ret)

[gremegity]

At what stage is it better to drop off lower-level set pieces for non-set items with a higher i-level? My guild has started our venture into Heroic HFC, and seeing the items drop makes me wonder.

For instance this is my pally: us.battle.net/wow/en/character/black-dragonflight/Biiru/simple You'll notice that his gloves are 670 while the rest of his gear is heroic BRF or better. I do have a pair of heroic gauntlets (Flamefury Gauntlets, Heroic: wowhead.com/item=113925&bonus=566) available in my bags, but of course equipping them would mean breaking the 4-piece set bonus on t17. When should I switch over?

I could use some advice.
Thanks
(PS Sorry, I'm too new to be able to post links, so I had to plain-text them)

[Urthearso]

You dont, they even have a socket. Switch to t18 2p only.