They just need to reduce the amount of damage that an assassin//shadow can do while in Tank stance and in turn add more threat to each ability to keep the tank viable in PVE. If they do this, the assassin will have to either Spec into a DPS spec where DPS gear should be worn, or stay in Tank gear... like they should be.... in a *mostly* tank build.
The fact that the class is able to be in full DPS gear, while still having all the defensive perks of the tank tree (and mitigation bonus of tank stance) is the major problem and gives it a huge advantage over every other class. Assassins and Shadows can still produce great damage while in tank stance/dps gear where other tanks simply can't. You could argue that this is what makes the class unique but you can't deny that it doesn't give a big advantage in PVP.
And yes: There is a lot of balancing that needs to happen. Smash is out of control, Marauders have too many tools//team buffs where other DPS classes do not and Sorc/sage Bubble Blind hybrid giving little to no resolve and is able to be clicked off... Are all things that NEED to be "balanced". ((You could even argue being Rooted with a full white resolve bar as another thing to add to the list))
Merc , Sorcs and Operatives all have to spec a specific way to actually be viable and desperately need help in the DPS survivability area. (healing is another story... operatives are TOO good, while mercs are non desired...and sorcs are only really viable if they're bubble blind spec)
Assassin/Shadow Tank hybrid does need to be tweaked because right now, it is way too strong. I have one and am fully aware that it needs to be balanced.
Do I think it will happen? Not really. I think the Makeb patch is going to do more harm then good because the Bioware development team has no clue what its doing when it comes to "balancing".
Quoting this because it seemed to get lost in all the pointless posturing, memes, and trolling. This is probably the most objective, accurate assessment of the issue with tanksins I've read yet. Too bad BW won't see it, and even if they did, their development team is simply too incompetent to figure out a solution.