I play most of the game solo myself - and I really love my tanky / stealthy Assassin.
I mainly just spam my AOE attack (that with an inquisitor you can basically keep casting, unlike a warrior who needs to build up the rage) - Stealthing is awesome (especially if you want to just whip through parts quicker) even though I still find myself just fighting everything because I enjoy the combat. You can vanish to get out of unwanted battles too which is a nice benefit too.
One thing though - I REALLY enjoyed the Sith Inquisitor storyline. It was completely chaotic and confusing and odd - and I enjoyed playing through it (I have a 57 and a 60 Sith Inquisitor). It would be worth at least to catch up on how your character came to be (read chapter summaries etc).
Dependance on the companion will change in a couple days (when all companions can heal/tank/dps)- I usually had Tweek set on healing myself, otherwise you could be a little squishy out on your own.
Rotation was fun - I never really try to min/max anything, I just focus on the fun of playing. I didn't really focus on gear for secondary stats, tanking in dps gear with a healing companion does help with damage and you're usually OK.
Feel free to let me know if you have any other questions - I'm not a PRO player, but if you just play Solo for the story / KOTOR 3 experience, that is the boat I'm in too.
tl;dr - its worth it to have the ability to Force Lightning people who annoy you in conversations. Much fun