My feeling is that while damage-dealing and healing do go back to pre-computer RPG designs, the notion of a "tank" role is something unique to computer-based RPGs.
Tanking is a gameplay concept that flows from an earlier design choice not to implement collision detection between NPCs and PCs. Once you've made that decision, NPCs are easily able to attack the characters playing the typically weak healer and caster roles. And once they're down, a total party wipe usually follows. Not fun. So as a quick-and-dirty "solution" to that problem, MMORPG developers came up with the notion of "aggro"... and poof, the tank role was born.
The point here is that collision detection is purely a problem for computer RPGs. In a non-computer roleplaying game (e.g., tabletop or LARP) where the live players are expected to know and follow the rules of play, you can simply say, "I attack Darg the Evil with my broadsword," or plop down a die-cast figure on a scale map of a dungeon, and that's that -- you get to soak up damage. Any physical damage-dealer is also automatically a "tank," so no one ever thinks of them primarily as fulfilling that combat role.
Explicitly designing character classes to satisfy a perceived need for a tank role thus shows up only in computer-based RPGs -- specifically, in MMORPGs where the rules which tell attacking NPCs what they can and cannot do physically must be implemented in code, and where one of those coded rules is that characters can pass through each other without colliding. (This may actually be a result of the developers choosing not to implement collision detection -- same result.)
If there's no need to code an "aggro" workaround because physically tougher player characters can physically get between attackers and weaker player characters, then there's no need to design player character classes around a tank role for attracting and holding aggro. More broadly, designing Tactical and Science and Engineering department-based abilities around tank/nuker/healer roles -- for no other reason than because other MMORPGs decided to implement those roles -- would be to embrace precisely the kind of foolish consistency that Emerson warned us against.
Aligning character abilities to certain preconceived gameplay roles isn't wrong in and of itself. It's only wrong if those roles are adopted as conventions, if they're merely copied from other games without asking whether they help communicate the overall conception of this game set in this unique universe.
Which returns me to my overall point, which is that if the action in Star Trek Online should be something more than non-stop destruction, why design character abilities around purely combat roles at all?
There will be more than enough challenge in balancing character abilities specifically designed to support Tactical/Security and Science/Medical and Engineering (and Command) gameplay without also having to try to shoehorn them into the tank/nuker/healer roles copied by other MMORPGs.
