I didn't found this by myself but nobody posted it here yet and I found it's very useful so I decided to post here.
If you're Horde and want an Old Ironjaw, there's a place which is quite difficult for Alliance to spot or attack you. I'll tell you how to get there.
First, go to the forge in the middle of Ironforge, you'll see 2 big wheels one on the north and one on the south. Jump into south wheel lava pool, you can also do the north but the south is safer since it's more difficult to spot and to be targeted than the north one.
After that, swim to the wheel and hug the wall so you're between the wall and the wheel and then spam jumping+moving. You'll notice there will be some invisible wall preventing you to get up on some place, go next to it and then jump on those invisible ledge. There are more than one ledge so you could pick the one you think it's the safest or easiest to fish.
You may fail to get on the ledge on your first try, when you come back, just don't accept resurrect yet, try to get on the ledge as ghost before accepting your revival.
Here's the example images of the location
If there's moderator who think that standing on the invisible ledge to avoid damage from lava and to avoid being seen by opposite faction isn't an exploit, feel free to move it to guide section.