A guildie OP healer confirmed to me (we in mumble). KD SA and his UW SA procced twice/together while spamming hots. I wish i had KD SA (i only have UW SA and UW BA) so i can not test it myself for Snipers.
UW SA and PvP Conq SA is what I am using right now and it procs twice/together when i sit in cover with the self-heal talent.
I can post screenies if needed (when i get home). I (think i) remember they removed this bug some patch ago and now it's back.
While I don't know if healing can proc both, damaging skills definitely don't.