1 problem with this is what if you like to do raiding and being socialable. Having incentive for FCs to clear raids will either force cliques within FCs or cause people who would otherwise be fine in normal everyday FCs into raid only ones just for those extra rewards.

Believe it or not ARR and early HW had very social raid areas, loads of talking in Wineport/North Shroud/N.Thanalan/Hinterlands, you also had inbetween instances sections where groups could congratulate each other, what killed it off? allowing to queue into raids from anywhere, once this change happened you only saw people as they unlocked things or in Hub areas.

I don't think adding extra incentive for doing savage raids/Ultimates for FCs is a good idea However if the rewards were titles only I think would be fine.

Actually surprised SE hasn't done something like World 1st titles for Ultimates.