I soloed a Star Fortress on my commando with a lvl 25 comp. It was hard, but possible. I tried the same thing on a sage with equivalent gear and lvl 27 comp and found it to be almost completely impossible. I tried every combination too. When I went healer, my tanking comp wasn't killing adds fast enough and we got overwhelmed. Healing spec with a dps comp didn't work because I simply could not keep my comp up through the damage. Balance spec didn't have enough direct dps to burn waves of skytroopers and got overwhelmed. Telekinetics came closest, but still couldn't stay alive long enough to get the job done since the comp heals are almost worthless now.
My opinion on the comps before this patch was that they were pretty OP at lower levels, but came close to balancing out at high levels. Now they work fine in low-mid levels, but are very underpowered at higher levels. Definitely more balancing needed.