If i remember right it was because MNKs can get 100TP from relic knuckles using Asuran Fists..and if you mean "nerf" i would have to say everyone got nerfed then. Rampage was nerfed, Slug Shot was nerfed, Raging Fists was nerfed, Dancing Edge was nerfed, Blade: Ku was nerfed, and even Gullitone then, not just Penta. Spamming WS was not limited to DRG and is not their strong point...if you actually see parses post TP fix, DRGs were top in the line with their wyverns.

If you mean the TP fix is what nerfed DRG, then every melee job that has a multi-hit WS that was of any good was nerfed too.