Are you using CC? Unless you're running Guardian/Shadow/Vanguard/NotASmuggler or the Empire equivalents, your group should have at least one method of keeping an enemy out of a fight for a minute at a time.
Commandos can Concussive Round anything.
Sages can Force Lift anything.
Sentinels can Disable Droids.
Smugglers can Slice Droids.
Scoundrels can Tranquilize non-Droids.
This isnt always the case. First boss in Mandalorian Raiders has two adds that cant be cc'ed and are untauntable. So 1OT with good DPS or 2 smart DPS to burn down ads asap is nice. So far tanking has been different in this game for me and requires some adjusting but its still incredibly fun.