Tanks and DPS are working the progression from different ends.
DPS kill priority is:
Normal -> Strong -> Elite
Tank threat gen priority is:
Elite -> Strong -> Normal
When I am DPS, I expect the Tank to ignore Normals (2-3 cooldowns on mine drop them), and I take it upon myself to pick up a Strong if it gets free from him. Better me than the healer. I, as a competent, appropriately geared DPS player, should have no problem dropping Normals and Strongs. Once they are done, then you hit the Elite.
When I Tank, I expect DPS to dirtnap Normals immediately, and while I do make sure that I gain initial aggro on Strongs, and keep it up as allowable while maintaining threat on my primary target, Elite(s), I know that a competent, appropriately geared DPS player can take down a Strong with little issue if need be.
Group dynamics are different in SWTOR than any other game. DPS have a more important role due to the nature of pulls. Anyone who tells you different is selling you something.