Missions ending with bosses are not fun in anyway what so ever. It's either vs waves of enemies or fight a single boss who is a BULLET sponge.
I've spent the last TWENTY minutes shooting bullet after bullet into the bosses head and he's not even down to half health. This is with a full fire team also!
It just isn't fun. I dread strike missions now, clearing a schedule just to kill one boss isn't fun it's tiring.
Edit: People are saying "bosses ain't hard" etc. It's not about being hard, it's about the grind of 20 mins shooting a single enemy in a tiny arena. It doesn't take skill to defeat the enemies but time instead
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If you have the skill to take on a boss that takes 20 minutes of sustained fire to drop half his life, then take that skill and get better weapons. Better weapons will allow you to kill them in 10 minutes or less. If you're exaggerating, well it's all your perspective and your impatience would lead me to suggest playing something like Clash of Clans or maybe Candy Crush...