I have never heard about 'two schools of fighting' I would suggest you are mistaking tanking versus dps. It makes sense to have tank make sure that the strong target is focused on them, while dps kill the weak targets. Perhaps you need to look at this from healers point of view. What would you like to happen if it was you who had to heal the group through an encounter.
I don't know about 2 schools of thought in SWTOR (because weak to strong is the only right way, considering TOR's mechanics), but strong to weak was the killing order in WoW because in WoW at least, back when I was still playing - strong mobs hit significantly harder than weak ones. and then the game changed to AoE fest and it became less important what you killed first, since you just spammed your AoE abilities on a tight group of mobs on every trash pull.