Oh yeah poetics I can see, goetia are way too valuable to waste on ventures imo. If you have a BLU you get a fair amount of ventures every week doing the carnival, it's like 540allied seals and 490poetics or whatever the numbers were, the allied seals buy you 130ventures a week and you can throw the poetics on top for a few more. Granted that won't cover your needs if you're spamming quick ventures on all your retainers but it helps quite a lot for less than 10mins of messing about.
I still would desynth, it's more money most of the time, at least until the price of sublimes really crashes.
Cordials can be bought with money, they used to be dirt cheap, not sure now but probably still are(less than 800gils), you can also craft HQ ones which are much better or buy Hi-cordials with yellow scrips which are even better and pretty easy to farm with custom deliveries and such. Same for materials, can buy them, gonna be a better tradeoff to get 2 sublimes, sell them, then buy 99materials or more with that money than trade in the item for 1500seals and buy like 10materials. Obviously you don't get sublimes all the time but their values is high enough that it edges out GC seals very easily, plus even when you don't get sublimes you still get some stuff(2k ingots or whatever, 10+k if HQ depending on type and market, plus some crystals and clusters).
The only real point is ventures but you can farm a fair bit of ventures everyday/week using 15centurio seals bounties(daily x2 with ishgard+kugane/rhalgr, takes less than 10mins if you only do the 15seal ones), 100centurio and allied B rank weeklies, beast tribe daillies if you feel like doing that, BLU carnival weekly and maybe leves although these tend to be kinda shit. I'd also heavily consider calculating exactly how much the ventures are worth(if you do quick ventures, you probably want to calculate a low average for the garbage you get back) and wether they're worth it.