I'd just go for this set: http://ffxiv.ariyala.com/UA9Z

It's the set that Dervy is aiming for and just use whatever i240 weapon you can get your hands on. That way, Pre-A8S is exactly the same as Post-A8S, only a Midan Spear swap. Chances are, Relic will be customisable and would best be invested into crit/det and there's a high chance Nidhogg weapon will be i240 Crit/Det. If it's Accuracy/Det, then of course, we'll have to see which is better :P