What puzzles me is that, back in vanilla, there was probably one shadow priest for every 4 raiding guilds on a server (raiding back then took even more time and dedication). So I can't imagine why would they build this around a 5% SWP bonus (which isn't anything decent, even back then). The items themselves were good, all of the items being on-par with BWL and AQ20 gear, and allowing you to stand ground long way into AQ40 and maybe Naxx. The great raiding bonus for shadow priests came with the BC, by making Vampiric Touch provide 5% shadow damage in raid-wide mana regen, and then again when Shadowform came to provide passive raid-wide spell hit (now haste).