The ammo stations re-activate very quickly so ammo can be gathered.
Just keep taking pot shots to keep the shields down while going to the stations.
My Fire Rosie did take the 1st phase (Eclipse?) out (after the shield was down with the Vibrapulse).
Those lasers did nothing against the 2nd phase (EOS). They are both beam (pretty sure), so limited range. I did have a few other lasers. One was an ice blaster, that did nothing to EOS, but ice is not the best against bosses anyways.
I was playing as Claptrap. With Flakker and Fragnum and a few NE glitch guns, the T4s-R did way more damage even to the health than any of the others. The Flakker and Fragnum were nigh useless except for going through ammo … and I did wait for close passes where I could see it was hitting … and only used them after the shield was down.