Arcane Echo --> Echo Question

Suppose I have Arcane Echo in slot 1, Echo in slot 2, and Blessed Signet in slot 3. I cast the skills in the following sequence:

(at time T) Arcane Echo (finishes casting at time T+2)
(at time T+3) Echo (finishes casting at time T+4)
(at time T+5) Blessed Signet (finishes casting at time T+7)

At this point, I know my skill slot 2 is filled with a Blessed Signet and will revert back to Echo at time T+27. But what happens to slot 1? Does it now have an Echo in it, or a Blessed Signet? Also, another question: suppose it does have an Echo in it, and I cast the Echo in slot 1 at time T+10 and then a Blessed Signet at time T+12 (which finishes casting at time T+14). The Echo in slot 1 will then change to a Blessed Signet. But when will it revert back to Arcane Echo? Will it be at time T+24, because that's 20 seconds after the Arcane Echo transformed into Echo? Or will it be at time T+34, because that's 20 seconds after the Echo turns into a Blessed Signet? Or what?

when you cast arcane echo followed by echo it will turn into echo. Then, you use blessed signet and you have echo/blessed/blessed. Use echo again, then the recently echo'd blessed, and you have three. So, to answer your question, yes, it works.