Yeah, i also have tanking characters, a jugg and a vanguard....iv always understood the role of tanking a bit differently than others, from wow
a tanks job is not to hold aggro
a tanks job is not to stay alive
a tanks job imo is to make the healers job/life easier.
thats what i always keep in mind whenever im tanking anything
this is probably because iv been healing for a good 10 years now, in different games, on different characters (first a rsham, then a priest, now an operative)
A tank's job is to do all of that.
They're supposed to mitigate as much damage as possible (i.e. stay alive and make the healer's jobs easier), and maintain aggro (holding aggro + making the healer's job easier).
If a tank's not holding aggro then your group will fail. If your tank has low damage mitigation and doesn't cycle defensives properly, your group will fail.
Conversely if the healers can't adapt to the situations and keep the group up, then you will obviously fail.