as far as i know as a smuggler/healer the only interupt i have are flash and dirty kick what ever this mob is useing dosent have a cool down and as someone pointed out he spans this AOE attack. interups only by time in this case too little too late; i alway die before any of my interup cool downs are up. i can't get Corso out of the blast zone fast enogh to avoid hits. all it takes is 2 hits and corso's out (fallowed by me).
Better take a second look at your abilities, smuggler "official" interrupt is called "distraction". Thats a third you can use (12s cooldown). Its melee range though.
I have just taken on this mob on my lvl 36 scoundrel healer (same level as captain Jesh himself), did it on first go although he downed Akaavi Spar. I did notice that he seemed to be doing more damage than 'normal' elites and that his flamethrower seemed uninterruptible. I did it on first try so I didnt have time to check whether I just fessed it up somehow or whether the flamethrower really is uninterruptible.
note: I have relatively good gear for my level with custom gear and mostly blue mods (I have three 50s incl. cybertech and artificer so I can keep my alts wellgeared and looking good). Spar only had her starting gear though. My character also has all the class buffs.
My first advice if you have trouble with this would be to check if you gear is too lowlevel or bad, or if your build is trying to be too "hybrid". Soloing this mob is definitely doable.