In regards to the question of WHY the backlash damage of Shadow Word: Death is dealing more damage to the Priest vs the target is 100% based on your maximum health which incentives you to NOT use it if your just helping the enemy kill you faster than you kill him lol.
Let’s say you have 10 million heath.
5% of 10 million heath is 500,000.
So that means if you do not at least do 500,000 damage to the target with Shadow Word: Death then on a 1v1 fight simulation, you are assisting the target in killing you faster than you can kill them.
So let’s say instead of the backlash damage doing 5% of your maximum health, it instead deals 10% of the damage done by Shadow Word: Death. That would result in the 500,000 damage example to only be 50,000 instead which is significantly lower.
Then let’s take for example you dealing 100% more damage to the target based on some raid encounter buff. Now you would do 1 million damage and backlash damage would still be 500,000 based on 5% of your maximum health or 100,000 based on the amount of Shadow Word: Deaths damage dealt.
So that means the more damage you do, the more in favor the based amount of backlash damage done to you is calculated on your maximum health. The less damage you do favors the percentage of damage done calculation instead.
So no matter what, if we can’t choose what calculation we are dealing with in terms of backlash damage then you will suffer more/less pending the situation accordingly.
In terms of Shadow Word: Death just not doing enough damage then sure, that is exactly why the backlash damage is noticeably more than the damage dealt. But as the expansion goes on and you get more gear, that gap will go lower… if the maximum health doesn’t increase the same relative to the damage being done.
At the end of the day, the backlash damage calculation just needs to have a choice built into a talent option imo then you can change based on your preference.
If we are going to choose how we want Shadow Crash to behave then I don’t see why this is an issue.
Otherwise just make the backlash damage be determined on the amount of damage SW:D deals and limit it to a low 1% and call it good.