Visualize "dice rolls"/background mechanics
Chance to apply effects or miss, and other calculated and somewhat hidden mechanics would be much more satisfying if they were transparent to the user. If you visualize what is happening for the calculations is easy to accept that spell didn't stun or that point blank attack missed.
I'd suggest something similar to Pokemon Duel, where an easy to see and understand "spinner" that shows the proportional split of chances. You can easily understand that there is a small chance to miss, but it landed there.
This could be extended easily for more complicated systems with saving throws, showing separate spinner for saving throw and for attack. You could also show default "spinner" chance and shrink or expand based on modifiers like terrain and list them above it.
Stun factor : 100%
Wet : +20%
Resistance : -60%
Spin with a 60/40 split wheel of stun or not stun.