Compare the time Method has spent on bosses vs. the time Blood Legion has spent on bosses. It is highly unlikely Blood Legion beats method to the Lei Shen kill. I suppose it would happen though. BL killed, what... 7-8 bosses pretty much before the European servers were even up. Method made up that difference and passed Blood Legion during the first week.
Also, Lei Shen isn't the last progression boss. He may or may not end up being the hardest.
---------- Post added 2013-03-22 at 03:21 AM ----------
Also, given another reset of gear... I doubt the 4% rumores were true... unless they got that absolutely infamous terribad 10man loot streak or something (like my guild did this week... literally 6-8 pieces of spirit/int mail with nobody to give it to) and basically aren't any stronger than they were before. I suppose that would be easy to determine with some armory snooping. They also probably had some sort of plan in place to attempt to funnel gear.
Especially with the thunderforged differences... if the bosses are truly difficult and tuned evenly... Paragon's chance of WF decreases with every reset as the 25s will further and further outstripe their gear level. They're already ahead.