The World of Darkness was definitely a step up in difficulty in comparison to Syrcus Tower. The bosses in there are relentless and have a crap ton of mechanics to boot. Surprisingly most of the mechanics in the WoD come from the Second Coil of Bahamut (the pre-nerf version) and adds new ones to the mix. Petrifaction, Fire-and-Ice dragons and Blighted Bouquet make a comeback! All in all, it's stressful since you need to be able to hold up on your own (indivudual awareness of the battle) as well as work together with everyone else (or else you may cause a wipe).