Players are strategically taking advantage of having heroes maxed at Damage reduction then increasing beyond the 50% Max by using rune effects sometimes over 100%. The game allows it so why not some may argue. It's not permitted in campaign so why is it ok in PVP?
I don't believe the game should allow it as it makes it unbalanced. It's no different to allowing 100% dodge or having 100% evade which I understand the game does not.
We can view the type of runes being used by defending heros but not the stats or the rune effects to decide if it will be a fair competition.
No doubt this has been mentioned before and needs to be mentioned often until bug fish put things right.