Don't know if it's the dumbest but it's definitely on my top 5. A few days ago I did the crota raid with two buddies and I was swordbearer with my bladedancer. I died from crota two times because I didn't go invisible even though I hit him, i was getting frustrated and was sure it was lag since I've seen that exact thing happen before, until one if my friends checked my perks and started laughing, I didn't have the correct perk activated. I think they will remind me of that everyone we do crota for a while...