Yeh the signets are kind of a pain but I found mine in a lvl 3 quest with some other people....it's one of the big open area ones...not kobold assault but something similar and a bit higher level lol anyhow we zoomed through it since they were a bit higher than me and I grabbed a signet so now I'm level 3 out of 8
so I guess you can just do that quest over and over real quick to unlock all the levels?