This thread was first posted in 2016 so I'm a little late to the party but I'd like to share my two cents on this. Firstly if you compare your average Trooper with your average Sith then the Sith would come out on top most of the time. However the protagonist Trooper you run in SWTOR is anything but average - firstly contrary to what many believe you are in fact a force-user. You'll notice that you can activate holocrons and on a specific Flashpoint (can't remember which one) you are seen commuting with Force ghost and a Jedi master (of Yoda's species) notes that you have a connection to the force. While raw and untrained this connection to the force puts you on a closer power level to other Sith. Consider the last chapter which takes place on Corellia - the Imperial Guard is specifically dispatched to eliminate you which means you came under the attention of the Emperor himself (this is further confirmed in the KOTET and KOTFE). Another thing that happens on Corellia is that your missions will see your trooper take out multiple Dark Council members which have been sent to Corelia - if that doesn't prove that the protagonist trooper is on par with a Sith lord I don't know what is. I understand that all this happens within the game and game mechanics and balancing allows for troopers to face up to force-users however this would also make sense outside of game mechanics. Outside of game mechanics the Trooper has more options available including a large array of meele weapons to chose from such as vibroblades and shock battons. As I mentioned above your force affinity would protect you against force attacks like lightning and force grip while supernatural augmention (granted by force affinity) means that your trooper could brush off being force pushed into a wall. Another thing to consider is that while the movies and TV series focuses on a later timeline when the rule of 2 is imposed for the Sith - the Old Republic Era has tons of Lightsaber wielding force users on the battlefield so fighting styles and additional training to defend against force-users would be incorporated among soldiers. Ultimately what you should consider is the protagonist in SWTOR (regardless of class) is an exceptional character with great force affinity and power.