unfortunately since Materia is relatively new and is isolated in its region, you probably won't have much luck there until 7.0 drops and new players funnel in. it sucks, but that's what dropping a new dc post expansion release gets you Dynamis on NA has the same issue, but at least there it can be mitigated by dc traveling. i feel like it'd be a good solution to temporarily allow dc travel from NA to OCE (and vice versa) to mitigate this in the same way Dynamis does, but until something like that is implemented and/or 7.0 drops, you're kinda stuck unless you world swap to Aether, Primal, Crystal, or, from what i understand, Goblin on the JP data centers (since it was the primary OCE world besides just going to NA data centers before Materia released)