Hello! Not only runes but any offensive spell shares a minimum cooldown, so if you use them right before an auto attack, you'll delay the auto attack in one turn.
This mechanic can be even used to kite monsters and take less damage.
To set an example, let's imagine a situation where you're 1v1ing a monster. Every time you hit it, you have a 2s cooldown before you'll hit another auto attack on it. Meanwhile this 2 second-delay, you can use any offensive spell or rune, but if you do it on the last 0,5s (at average, cannot tell the exact amount of time) you'll cancel the next auto attack, delaying it a little bit further.
Not only you have this cooldown, but also the monster share the same characteristics. So if you time it out right, you can walk one or two sqm to get some distance and avoid getting hit while you're on "recharge" time. It is not really useful, since in many places this will cause you to lure other mobs, but when you're in a place where there are only the two of you (you and the monster) you can get to avoid some damage doing that.
When you're fighting a distance-user mob (e.g. lizard legionnaire), sometimes you can notice it will cancel an auto attack because it is moving at the exact moment it was supposed to attack. When you're a paladin or a mage you can notice it a little bit clearer, since you'll kite quite more.
Hope this little piece of knowledge can be found helpful. Any doubts I'll be happy to help. Cya :)