Right now to get on (almost) every raid group in sod, you need to be much higher gs then this content drop (900+gs for nightmare drakes or bwl, that drop t2/t2,5 gear, and 900gs is aq+ itemlevel). So only soluation is to cheat with your itemlevel such as use ony attune BoP neck that gives very big gearscore (as its broken calculation and gives +100gs compared to alternatives), or use some FR naxx craft pieces that are high gs but dont provide set bonuses (so in fact, lower your dps). But i don’t think it’s good to cheat, and without this cheating you simply can’t get into raid if u are lower ilvl then this raid.
Easy solution to fix it. Add to every hardmode of the old raid, mechanic same as on ALgalon-10 achievement in WOTLK. You get hardmode loot only, if every player in your group is not higher then some ilvl (on Algalon your every piece should not be higher then some ilvl, but i think better to do that system counts your avg ilvl so you can replace only some pieces with lower ilvl blue AH gear pieces, and not change all pieces; so it’s not hard to do and change 3-4 pieces for greens/blues if you are overgeared).
To prevent calculating or just inattention fails, a buff will be displayed on person if he meets this itemlevel req, so it’s easy to check. When every players have buff, they should activate the hardmode (add an altar so all players click on it) and from this moment if any player switch gear and will be higher ilvl then max possible, he will be insta teleported out of the instance (or just getting an error trying to equip gear that brings him higher then set max ilvl).
As blizzard said sod is experiment, so its a good place to test such system. Thoughts?