Having played a sage, a sorcerer, and several others, ...
I'm not sure what the problem is here.
Khem and Qyzen's ai operates no differently than T7's or Vette's or even that lughead with the trigger-happy harpoon, Corso.
Are we talking solo play, group, or are you having this problem in both?
The basics are that by default your cpompanion does not attack unless you attack or are attacked. If you take damage, the companion will (unless on passive i.e. ctrl-2) attack the mb who attacked you [and then proceed to any/all mobs that subsequently attack you or the companion for engaging their 'group-mates']
This is true for all of them, in solo and groups. In groups, your companion does not attack mobs damaging your group mates by default; they must damage you, the companion, or have you issue an attack command [ctrl-1]
Is your issue/experience something different than described?
Because otherwise, that's just comapnion ai in general, not healer/khem/qyzen specific
heh, I know the frustration. Seems so obvious to meI keep expecting it to be in the ai -- if you're in a targeted aoe spot ... move.
ah well. for me not a biggie, nut I feel your pain.