I apologize for only reading the first page before replying. That said, assuming you're serious I will offer this input. I too was feeling abit discouraged with my commando during the 20's. I have taken the gunnery tree and found myself feeling particularly squishy. I made a few changes, gained some levels and the problem has more or less sorted itself out. Few suggestions, and I may be giving bad advice here.
1. When choosing gear, if you solo then don't always go for the obvious dps increase. You need hp and since you don't have a shield generator having defensive secondary bonuses in your gear is an asset.
2. Aric is a great companion, and geared correctly a dps boost, however I at least found Elara a more effective. She keeps me alive better then Aric's dps did and her shots actually aren't bad dps.
3. Take the talent (sorry, drawing a blank on the name) but it increases endurance by alittle and healing received by a lot. You end up with 2% more endurance and a 6% boost to heals received. As you fill in talents taking the 2% boost to heals given and received and from another tree the 3% boost to your endurance I feel will help also, but that's long term.
4. Have faith, it will get better. Whatever my issue was in the 20's some gear upgrades, some new talents and working with my pet healer and I've gotten very happy with my Commando's performance in his 30's. I believe you will to.