Why does it say I've defeated 0 mobs when I have?

I will go ahead and post on the minecraft forum as well. I did defeat the ender dragon but the overworld hostile mobs were spawning before that and have continued to spawn after as well. The overworld hostile mobs are also spawning in the nether everywhere.

I believe it's not the weapon level but the player level affecting this.

• 4 lvl or lower below mob: 100% damage penalty
• 3 lvl below mob: ~52% damage penalty
• 2 lvl below mob: ~42% damage penalty (guesstimate since I didn't have the gear to put me to lvl 22)
  
• 1 lvl below mob: ~32% damage penalty
• 0 lvl below or higher than mob: 0% damage penalty
  

Source:
https://www.reddit.com/r/DestinyTheGame/comments/2h9t6b/this_is_how_light_levels_affect_your_gameplay_and/

I've watching some gameplay videos of Skyrim, it does appear that the Dragons have a HP bar.. at top centre of the screen. But, I don't know about any of the other Mobs. Just what I've seen.

But they she no details and when it say, 0/8 strikes? Why no warnings, and why no details?

It depends. I start on peacful sometimes to get a base going. As far as difficulties beyond that, I like Normal. Hard doesn't seem to spawn as many mobs and I like to see my mob traps working. After I get my base built I usually move it to Normal, but
I'm thinking of starting a new world and having it just be on normal. I've noticed griefers are less freaquent if when running around at night they are constantly overrun by hostile mobs.