had to kill one several times... each time I would move further down the ramp. Finally he died and stayed dead, but then the boss aggro'd me right away
Is this a bug or is it normal?
After a wipe, I've had the last two trash mobs constantly respawn on me too. It's deeply painful. They do eventually stop respawning, but by that time I'm usually out of mana!

It's a bug, and I'm pretty sure I saw it mentioned in the WowWiki article for this encounter.

ps- note small, relevant quoting technique