In the description of the skill it says that you're supposed to end up behind the target, but when there's no room behind the target you end up on a random free spot close to the target.
On some other skills like Teleport you can't teleport someone that's effected by things like Fortification and you just get red text saying "Invalid Target"
How about doing that to the Scoundrel's Backlash skill when there's no room at the same elevation in the back stab indicator cone behind the target to make it true to the description and to prevent this from happening..
http://i1266.photobucket.com/albums/jj525/kimhj1/20180404175740_1_zpsyahdmrof.jpgRed Prince started the Backlash attack where the red circle is, as you can see there's no room around the target anywhere, but where he was standing. And instead of it ending where he was standing when the skill was used, he ended up on the higher platform behind the target and being unable to make any meele attack due to elevation difference.