This is not working, few item lvs. above the casual weapon is not an option especially when it gets deprecated few months later with the next casual 24-man raid.
It's not only the weapon, like I've said before, the whole raid gear should be ways more higher than the casual one with the help of end game crafting to push it in some way (the overmeld logic works but again it's accessible to everyone and that's not good at all). On the other hand, if the casual gamers had something to do they wouldn't blame about getting the same gear of raiders; truth is the lack of content is real and Heavensward was pretty much a joke compared to massive expansions such Aht Urhgan in FFXI.