I only played those dummies as SMN.
When i was ilvl 299/300 with a 290 ilvl Weapon, i was unable to beat both Suzano and Royal Menagerie dummies. It was something like 8/10% remaining for Suzano and 4% for Royal Menagerie.
You might have some windows of improvement, but unless you are doing something wrong, you'll beat this just by upgrading your gear.
Dont forget to meld the right Materia, too.