Elegy

Some pros mentioned for this buff, I have some disagreements however
You are looking at purely the regen on the sword:
The swords that give regen (Bonesword and Blood katana) are not taken because of their regen. They are taken for their high DPS (while you could argue blood katana needs a buff because of powercreep, maybe faster attack speed, w/e). The regen should not be the defining factor for these strong swords as they already offer so much else. 
You are looking at it from a pure wm perspective: 
Hybrid builds benefit from extra chakra, and although most pure wm's can run low chakra, most wm's are not pure. Tanks in this game already benefit from best scaling of stat points, offering a buff like this would give even more of an advantage Medic hybrids gain heals from the increased chakra On a side note, the regen is not just taken for in fight regen. Having constant regen while running around (incase of mobs damaging you, or some lowbie) and not having to stop to heal is a pretty nice luxury.