Observations and Suggestions for the 4 Relic Shield approach
I watched the NACL games yesterday, and you could see that the idea of everybody but mid going Relic Shield was spreading. In the first game, things were fairly normal, and in the second one team went for stacking Relic shields. They were basically even in gold at one point despite being down two kills and a dragon, but in the mid game they started repeatedly losing teamfights.
In the third game, one of the two teams went Relic Shields, and took a half jungler approach, where they'd clear part of the jungler and come back to top so they could both use both charges, and the cycle would repeat. The relic shield team had some big teamfight losses after pushing to the inhibitor turrets, which I think is a repeat of the earlier game, where there was a gap between where the gold advantage from the shields wasn't enough to buy combat items to stand up to the team that took a standard approach.
In game 4, everybody just bought Relic Shield in the long lanes, and there was basically no going outside your lane for a long time.
My biggest dislike about both teams going for the 2-1-2 approach is that it felt quite boring on the strategic level. There is a lot of choice and skill involved in choosing where to gank and when, and if duo Relic Shield lanes don't have a good counter by teams using a jungler, then the Relic Shield team can just win lane, and just keep pushing in.
They might not even want to group up, since they can stay in lane longer and more effectively, and the jungling team can't spare anybody to relieve pressure for any lane. The extremely small and early observations suggest that grouping up favors the standard team which has better synergy item-wise as a team, while Relic Shields have good synergy in pairs; having four people with Relic Shield group together isn't as efficient use of the item gold.
Suggestions The standard counter to sustain is dive/all-in, and I think that's a direction I'd suggest trying: get a jungler or top who can go all in to get a kill, or take Leona bot and go all-in at level 2 with Graves.
-- Use Heimer to push mid and take the tower since nobody is coming to gank you. Alternately, take a roaming mid. TF can kill minions, push to tower, and then gate down to bot if you can coordinate the all-in 3v2.
-- Maybe just concede you'll lose a tower and then group, since outer towers are worth less gold and no xp. If you take lane bully bot and shove them under tower, they'll use the Relic Shields to last hit under turret, but they'll still probably lose some gold/xp. If you bully bot and mid, you can put put money into damage items for your ad and ap carries, while the Relic Shields haven't generated enough profit to produce matching value in a teamfight. The whole idea of a carry came about because of exactly this: if they get money, they can itemize to do more in a teamfight than an enemy that hasn't focused the money toward an item power spike.
tl;dr Relic Shield is great for gold and sustain in duo lanes, but Face of the Mountain on four people isn't as good in teamfights. I suggest being more aggressive away from top lane and wanting more teamfights, especially at the power spike when the team with jungler has just gotten major combat items on the AD and AP carries while the Relic Shield team can't do do nearly as much damage.