I'm not a big fan of regen on Stalkers. The fact that Dull Pain is just a heal with a long recharge takes a lot away from the set for me. That said, the -damage effect from KM would work well with regen, helping to lower incoming damage to a point that your regen/heals could compensate.
Of course, you could say the same for Ninjitsu, even softcapped. Lowering incoming damage means the occasional hit that does get through hits for less. Still of the two I'd say regen would benefit a lot more.
Regardless I don't think there's enough synergy to favor one over the other. The -damage from KM helps any secondary.
The only synergy I think is notable is KM/DA with OG. I like stunning bosses.
-Cant decide what secondary to use for my new Kinetic stalker.
-I have it -narrowed down to regen and nin
-How does regen preform on a stalker?
-Does kin bring any synergies to nin or regen?
-plz help