I'm going to assume that you're still playing in pre-searing, and that you're encountering this issue on the other side of the gate. If I'm wrong, let me know.
I also play an elementalist, and when I first began trying to do that area, I had the same issue you're talking about... more and more charr piling on top of me.
I had to learn how to "pull."
What this means is that I got myself a bow. Specifically, I used the "Nevermore Flatbow" that came as a bonus with my game purchase. You can check if you get one too by typing "/bonus" (minus the "" marks) into local chat. If so, you'll get a bunch of weapons and a summoning stone which will give you a little fire imp ally who will help you fight. If not, I'm pretty sure you get a bow as a quest reward for the quest "North of the Wall."
With my bow, I learned to pay attention to the movement of the charr and their patrols on my compass map (the movement of the little red dots). I'd wait until it looked like one group of charr were sort of on their own, and I'd shoot off an arrow and run away slowly, so that they would chase me in a small group.
This then allowed me to fight them away from all the rest of the charr who otherwise were all too eager to dive in and slaughter me. LOL
There's a little information about pulling on the Wiki here:
http://wiki.gtm.guildwars.com/wiki/Pulling
It can take a bit of practice to learn how the charr patrol and how best to pull them away from the main group, but it really isn't too hard... just be patient with yourself.
Also, I don't know if you have permanently chosen Necromancer as your secondary, but if not, you might consider becoming Ranger secondary for a while and going and charming a Melandru Stalker. They're quite handy to have and will often draw the aggro of the charr so you can stand back and cast your spells.
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I realized I wasn't clear about something -
You don't have to be a ranger to use a bow. You just equip it in one of your weapon slots and use it for the pull... then switch back to your wand or staff for casting your spells after the small group of charr has chased you.
The requirement on the bow won't stop you from using it to pull, it just means you won't do much damage with it - but you don't NEED to do damage with the bow... it's just a means of getting the charr's attention from a longer distance than your staff or wand will let you cast from.