Wyverns are custom, tough monsters put there by Nasomi called OWNMs. They aggro Blood only (not sight/sound), drop stuff from the loot tables of various BCNMs, they sync your level accordingly when you pull them and you have a time limit to kill them after which they drop no loot. OWNMs were there while BCNMs were unavailable so we could still get that gear, but Nasomi decided they were there to stay even after BCNMs were coded in.
"/cm p" and "/cm l" work for me, I'm not sure why it doesn't work for you.
There's a bug where the combat log doesn't tell you about an attack's damage when it kills a player and no number pops up on your model. But something definitely hit you, whether it was an auto-attack or Bomb Toss or whatever, we can't know. =/
I don't know about the first and last bug you're experiencing, you may want to check the Troubleshooting section for clues:
http://nasomi.com/wiki/index.php?title= ... leshooting