Every class / player / spec / situation / fight has different considerations.
Assassin DPSers can stealth and rez out-of-combat. Assassin tanks never get that chance.
You shouldn't build your ops group based on who can exploit the game and get a ghetto-rez. The Ghetto-rez doesn't even work half the time in harder fights, because you will likely be thrown back into combat. It is completely ridiculous to base your raid group upon what would make it easier if you fail.