Borderlands – In what order should I put the skill points if I want to maximize the damage that Roland’s Scorpio Turret inflicts

Class Mods take effect as long as you have at least 1 point on that skill.

The points added from the Class Mod can stack to over 5 points adding extra effect. However, certain skills are not really worth putting more than 5 points into, such as Aerial Impact for the Hunter. I mean, whats the point of having an over 100% chance to stun enemies? That's just wasting skill points that could go to something else.

Taken from here.

An elemental weapon actually usually shoots normal bullets, that are exactly the same as that of a normal gun. However, sometimes they trigger an elemental effect, or "proc" (short for "programmed random occurrence" or "procedure"). When this happens in addition to the bullet damage, the elemental effect and damage is added. These procs can trigger with varying intensities, from x1 to x4, as seen on weapon infocards. Different weapons have different proc chances for each of these elemental multipliers.

Whenever a weapon procs, a certain amount of elemental damage is added based on the current element's damage multiplier:

Element Damage Multiplier

Incendiary 60%

Shock 100%

Explosive 150%

Corrosive 40%

For example:

• if a 100 damage x1 incendiary repeater procs x1, this will add a 1x incendiary damage multiplier (60%), dealing an extra 60 damage.
• If a 100 damage x3 explosive sniper rifle procs x3, this will add a 1.5x explosive damage multiplier (150%) dealing an extra 225 damage.

Taken from here and is also worth looking at for more information regarding specific weapons and their elemental effect.