For instance does gfalcon stack with wilber and is there a place I can compare different heros at
I’ll let someone else direct you a post that lists the hero effects that stack with each other, I know one exists on here–but the answer to your question is yes, those stack. Elemental defense debuffs and regular defense debuffs stack, but two of the same type replace each other. It’s not 100% fool proof, but I think of it in terms of the icons. If they have the same icon they overwrite (including an up or down version of the same buff/debuff), if they have different icons they probably stack.
I’ll point out one good resource on the forum for working out which status effects/ debuffs/ buffs stack with each other:
in terms of where you can compare different heroes at there are three great resources that I would recommend.
First is the Hero Utility by Razor, Second is the Hero Guide by Anchor (and the 7DD + friends crew). The last is a newer website which has the heroes but also allows you to filter them by effects.
Anchor (7DD) Hero Guide: