Sci char that can heal itself. You can't tank unless you can heal yourself.
Engi has limited heal and shield regen, and the generators can be destroyed. They're actually a huge "must shoot it" flag for any NPC.
Tac is the worst at tanking. It can only use hypos to heal himself once every 30 seconds, that's not tanking, it's respawning a lot. You do get the cloak as an advantage, but you ain't tanking much while cloaked.
Easiest to get lots of aggro > spam grenades and alternate fire on the tri-beam rifle.
If your "tank" is based on another dedicated healer you're basically taking out two dps-ers of your team instead of just you.
Cause a tank would be a toon, that maximizes is hitpoint and resists significantly to reliably pull aggro and survive long enough for his team to kill the mobs or bosses.
Easier with a healer in his back.
Now I don't want to tie this to a specific class and ideally want to be able to build class hybrids to avoid a strict trinity build.
But If I want to go so role specific I really can't?