[TheDemon]

Arcane Nexus is pretty much impossible to dispel and keep dispelled, since in games of a certain size it generates far more gems in one turn than it costs. Utterdark certainly can be dispelled, but were I a player who had high level astral under Utterdark, I'd simply let the other players suffer through it and cast Solar Brilliance every battle. Course that's not fully practical, but personally I don't think Utterdark is as much of a win button as it's made out to be.

There are a few nations that would suffer under the removal of gem gens. In my opinion, Oceania and Kailasa really suffer from loss of Clams, since not only are the nations tailored for forging them but they also rely on extremely expensive astral summons that are really hard to afford otherwise (wish and the Kailasa uniques). Most ages of Abysia suffer from loss of Blood Stones, as does most ages of Argatha. Marveri relies a bit on both Clams and Blood Stones. Machaka and Yomi both can really spam Fever Fetishes, although it's more rare since a large fetish farm requires an insane ammout of extra micro.