Item compatibility?

[eternalfire]

Is there a guide somewhere that shows what equipment is compatible with what unit? Seemingly there's an issue with compatibility as I noticed people with weaker equipment and worse units than I have higher defense. And this is not because they have more defense towers.

As a coincidence I was short 5 armor for pvp. When i added a mage armor 4attack 6 defense, theoretically I should go up 4 points for attack and 6 for defense. However when I check the raid result, my units used went from 40 -> 41 (expected). Checked and saw the mage armor being listed. But the thing is, my attack only went up by 2 points on my profile and defense (1 or 2) points. This might have to do with my army consisting of no mages and mostly machines...

Anyone have experience with this?