if you dont need speed, a 90% elemental is the best option.

Critical delay or point strike, just try ingame and find your perfect fire rate/damage ratio:
[Speed Trigger] with [Point Strike] give 1.87 att speed and 77022 dmg,
crit delay and [Vile Acceleration] give 1.8 att speed and 83530 dmg,
crit delay and [Speed Trigger] give 1.4 fire rate and 86550 dmg,
[Point Strike] and [Vile Acceleration] give 2.22 fire rate and 74335 dmg.

change primed cryo round for [Stormbringer] if you need corrosive.