On another threat I came to this conclusion with another user and I decided for me that the 340 alternative are BIS I don't care much for the mininum amount of damage gain you get from 320 pentameld.
so if we put a base od 4000 overall dps the difference in sets will be
Crafter 320 4096
Raid 340 4020
so the difference will be a mere 76 points? points that could be achieved by optimizing roations in the middle of the fight to squeeze more dps, sure someone with penta acc will be able to rank up avove in the top 10 fflogs but all that and at the cost HP and overall less base main and substats and 10kk+ gill sink. I'm really torn in what the community call these days BIS for tanks, I'm aware the dps meta left a big stain in our community but this is some extreme I can't comprehend, min/maxing is important but 90% of the tanks in this game wont even be able to use that extra 76.
the only argument I can get behind is what Aleph said
I can see this situation if you have the money to burn and wont get your full 340 right side anytime soon then you can blow it and be done with it, but at the same time I'd harldy consider the crated set bis, but otherwise if you aren't top raider aiming for world/server first I don't see why anyone with their mind would waste so much money in such a insignificant return.
so to get back at OP I don't think the crafted 320 piece being BIS is not that big of issue as you and many others make it out to be the I think SE wasn't balancing these crafter pieces thinking the overlass census will be to blow 10million gil but at the same time I'd agree that raid acc should have more str attached to them for anyone else if you don't have the money or just are not rushing to get your right side just go the 340 route IMO the hp helps liviate healer stress and smooth fights.
TLDR: the difference between 320 vs 340 is a mere 1.3% dps difference, which unless your name is on the top 10 fflogs it doesn't really matter or make any signiciant change at the cost of huge amount of gil depending on the server and overall less stats including hp making it harder for healers, but if you have the gil and no you are no were near on getting the 340 alternative is a quick head start. So it all depends on your preference and urge to have a quick bis. How effective each set is is insignicant as both are pretty much on par with 320 having a small dps gian.