To clear up any confusion, the report on BG cited a JP post, where it actually lists 天龍脚 as +3% WS DMG. These are Tenryu legs, not Khepri. Unfortunately, a mistranslation that people, including myself, were so excited to hear that they didn't bother checking the source themselves.
The augment is most definitely haste (6% for smooth synergy), making these pants not nearly as remarkable as before. They are certainly the best pants for SA Mercy, but Thaumas Kecks will still win for TA Mercy. As for TP gear, these have to have the full 6% haste -and- to be giving you a decent amount of critical hit rate from dDEX to win over Thaumas Kecks.
You shouldn't use Mercy unless its stacked, in most occasions anyway, So This is a clear winner for SA/Mercy. TA mercy, You have 3% Double Attack vs 10 Attack. Thats a bit tougher, Depending on the mobs Defense, I'd be tempted to go with These as well.
someone is reporting 3% WS dmg augment on these but BG is reporting 6% haste augment on these with Abdhaljs's Honor. I thought the augment was static with every cursed gear peice. I would have to make sure its really ws dmg 3% before I drop 60mil on the kecks and Abdhaljs's Honor. If it is ws dmg augment, will need to run tests to see if it works on the first hit only or all hits. (Since that shura kabuto was a disappointment and worked on first hit only). Won't be seeing HQ peices for awhile. Materials for these drop from Bismarck, legion final chamber mobs and abj from Morta. PLus the HQ rate and needed 110 craft skill and syenergy to augment these.