put 1 group on bombers that spawn up top in the rafters. Ranged dps works well.
Spindle's dps is pretty mean, debuffs work wonders in keeping it controlable.
Adds spawn from about 80% on with 4 at a time, steamwork menders, Kite and kill them all. one by one, then back on him.
about 50% two grates start opening, ya use ground spawn items to cast a buff on ya then click the levers to close em, or take nasty dots.
Around the same time mezzable clockwork gnome looking modles will rush the raid, mez them. Keep killing menders. Burn last 30% or so of spindle.