As always, questions like this depends a lot on a few factors:
- Player skills: I don't mean club, sword, etc... I mean actual skill in the game. If the team is good and knows what it is doing, then the requirements are much lower. In this case, all you basically need is a blocker.
- Number of players: more players means you can be weaker and it won't affect your team's strength overall.
With that in mind, the strategy for the fight is very simple. But people need to know what to do and how to position to avoid standing in the way of the players luring and to avoid taking free damage from dragon waves.
When the event was first introduced I managed to complete it on my level 80 druid, on mana shield. So, make sure you teach the whole strategy to your team. Hire a high level blocker and you should be good to go at level 100+. But my sugestion would be 130+, so players can use Ultimate Potions.
As far as I know, there is no level requirement to access the area, unless it was changed recently.