Since the game released, This same issue has been there. Neither the “Big Game” Hunter skill effect boost, nor the legendary stalker com’s hunter skill power boost, affect the interplanetary stalker’s damage boost. As far as I know, The unique stack bonuses are calculated correctly, such as the action skill damage or movement speed bonus. Even the other skills, to my knowledge, gain the respective damage boost from those two sources, such as frenzy, second intention, psycho head on a stick, the most dangerous game, and strangely even hunters eye, although it isn’t listed as a hunter skill. I have tried relating this to 2k support already, but they didn’t seem to do much about it. I will now provide picture proof of Interplanetary stalker damage not being correctly buffed:
Base melee damage without any guardian bonuses or skill bonuses. Just a basic unbuffed melee strike. (1338)
Now we add one stack of Interplanetary Stalker, (10% damage at 5/5) to get 1472. No big game yet, just the skill by itself, which is doing exactly what it should be at the moment.
Now, we get 3/3 big game, and did you notice anything? The damage did NOT change. Still 1472, which is 10%, rather than the 13% that it is supposed to be at after big games boost.
Now, we equip the stalker com, which has +3 big game and +2 interplanetary stalker. This puts interplanetary stalker at 14% before big game’s boost and the stalker com’s boost. And what do you know, we get 1526, or a 14% boost to the 1338 base melee! This clearly shows that big game and the stalker com hunt skill boost is not correctly adding their bonuses to interplanetary stalker’s damage. If it were, we would be getting a max of 25.9% per stack, which is after 14% gets the 85% total hunt skill effect bonuses. I’ve tested different damage sources such as the rakk or just an ordinary gun to get the same results. It’s sad, and quite a hard to notice issue without doing deep testing. Odds are, no one even knew this was an issue to begin with! As I said before, the unique stack bonuses get the intended bonus, as I can feel a sizable movement speed bonus when using the stalker com than without. Anyways, if you have any questions or concerns, let me know, but otherwise, please spread the work so gearbox fixes this for all those flaks out there.