VERY confused about elemental damage

Solution 1:

Elemental effects usually apply per shot, and often have a duration where they continue to do damage. Some do splash damage, but many don't, the variety is huge. Some explode, some leave clouds of effect, some are more or less effective with slag applied, and the ratio changes with each play through. In TVHM elemental damage is much more important against shields and armour, and in UVHM enemies take a lot more damage but slag is much more effective too.

On top of that there are class modifiers that can completely change how effective a gun is. For instance the siren gets lots of bonuses that help with rapid fire elemental guns like SMGs, making her capable of extremely elemental high damage per second while also setting everyone on fire.

Basically the only way to really tell which gun is best is to use it with your character and see how it works.

Don't worry which gun is best - new ones turn up all the time and your favourite awesome gun (that you did all the maths on and figured out was best) will probably be out classed in a few levels.

Solution 2:

It turned out to be a glitch that needed an ol' save n quit. Everything's in order :D