[Snake]

Making it do Darkness damage is also a good alternate choice in my opinion, since it gives more ways to resist the nuke damage.

Both 4M + Darkness damage and bam, this skill is balanced to an extend, because unlike Retaliate, this does physical damage. Though, it makes me wonder about the damage, will it really need to be reduced to '75 per rank' after such change?

In my opinion, due to Absolute Death, White Spirit, Holy enchant and especially FALLCALL, yes, it should. 75 damage per rank is the way to go in my sincere opinion.