What gives you this "I feel weak" feeling? all classes are pretty much the same at low levels, more so at 11. If you are having trouble killing mobs without dying, maybe you just need to update your gear (vendors if you havent gotten full drops, which should be common enough to keep you at lest on par with the planet's level, can do wonders and you dont have much to spend credits other than that and skills until 25). If you feel weak because you don kill as fast as the lightning shooting guy next to you, then that's just normal. In almost every mmo Nuker classes (or ranged DPS if you want) such as the inquisitor, always have a higher initial (and sometime final) damage output, and at low levels their weakness (being squishy) doesnt show because mobs die too quickly at first. The best advice I can give you is keep your gear up to date and always have your companion attack first to soak up some damage for you. Other than that, keep working those skills until you find a rotation that generates and uses up rage consistently allowing you to deal more damage and kill the mobs quicker. Last point of note, Cloak of Pain (if you have it yet, dont remember which level Mara's get it) is your friend, use it. (I have a 50 Marauder and a 43 Juggernaut, in case you were wondering)

I used Jaesa ever since I got her as Carnage Mara, Anni Mara and Hybrid Jugg, never had any problems with the class quests or leveling. Just need to keep her gear (and yours) up to date, and yes, you'll need to heal after fights, but you kill a lot faster than with Quinn. If using Quinn is overall faster leveling, I did not notice it. also, I use Jaesa with a single blade lightsaber, again, never had any trouble, quest content is easy if you manage aggro and get to know your class.

see, this is why people should not get high and post on the forums.

Other than was has already been said, my experience is as follows: Maybe you are doing it, maybe you are not, but managing aggro is very important as a Marauder solo questing. You need to let your companion take some of the damage for you. Let your companion initiate (a dps comp, not Quinn, I used Jaesa ever since I got her), and burst one of the mobs quickly (you should take aggro from it after a couple of skills), If at any moment (after defensive CDs) you are below half health, go Invis, this will reset your aggro and the mob will get back to hitting your comp, dps slowly as long as your comp hold, if she gets low, burst again, etc. This will work for any hard mob, even golden elites. Also, more importantly, you are probably not using your Interrupt. most of the Elites burst damage abilities can be interrupted, sure, they can usually recast it, but it will buy you precious seconds in which your DPS comp will still be hitting them. This includes timing Force Choke to interrupt, not just using it whenever. Lastly, for this particulat fight, I would go Berserk over Predation, not sure which one are you using, but Berserking with 6 rage built and just 6-spamming Massacre should down one of the mobs fast enough. I dont remember how I did it, but I remember not having problems.

none of her skills require a double bladed lightsaber, you only lose some min-max damage as someone said already, but it makes little difference in her overall dps. I use her with a single bladed lightsaber and I keep it updated, never had a problem, currently lv 50 in corellia. While it's true that Vette seems to have a better dps (and even if its the same, the fact she is ranged and stays out of aoe targetting you makes her a better option) you should have no problem leveling with Jaesa with a single saber, I did it and I didnt have any trouble, even vs quest bosses, just keep your gear up to date. Im a Marauder by the way, havent gotten to Jaesa with my Juggernaut yet, so no idea how different it is for juggs.