After pouring hours and hours into research on both existing lore and what gaps BioWare has been filling, I noticed something many people seem to consistently miss. Most players prefer to pair the current classes based on their group rolls, which is only natural for the genre. I think this is a mistake, although nobody's in particular. Star Wars: The Old Republic is simply a unique beast when it comes to class pairings and the story is to blame.
The recent info-trickle on healing contained one quote of particular poignancy here, "Several of our classes have healing branches that they can follow that will have some specific healing powers, but we don't want to make it a requirement for the base core game." Logic follows that if several classes out of the assumed eight have healing branches, the same could be said for other group functions like DPS, tanking and crowd control. Hybridization and incredible levels of class customization seem to be what BioWare is hinting at here, and that combined with the iconic pairings is what's responsible for the confusion.
A perfect example: The ongoing official forum discussions on the Bounty Hunter, and which Republic class it's paired against. The classic iconic paring is undoubtedly Smuggler, with the most famous example being Han Solo and Boba Fett. You wouldn't be wrong for saying these classes were a pair under that light, but they do not sit opposite one another thematically or mechanically. The Trooper does with its preference for heavy, experimental, expensive but ultimately versatile array of weapons and armors.
On the flip-side, the Smuggler wears very light armor and usually packs a customized, if not standard, blaster. Their fighting style is officially described as guileful and improvisational. However, when it comes to the storyline quests, Bounty Hunters and Smugglers will probably be seeing a lot of each other over the course of the leveling curve and well into end-game content.
I know I'll be going after Smugglers in PvP with my Bounty Hunter, especially people named "HanSulu" or some such thing.
So where does that leave the Empire's variant of the Smuggler archetype? Well, like I said, just because the Bounty Hunter and Trooper work similarly, doesn't mean they're going to play the same or even have the same exact options in combat. Likewise, a Sith agent or assassin class mirrors the Smuggler without being the exact same class.