It seems that the only attempt at a slow that ANET wanted to give us was the super weird chill proc on the hammer (I forget the actual trait).
I like the idea of symbols causing a slow but I don’t think that crippling people is in the guardians flavor.
We already have “walls” with the staff, hammer, shield and some of our utility spells so it seems that if we could expand on that we could be golden.
My idea is that we have a trait (maybe replace the hammer one) that says the first time an enemy enters the edge of one of our symbols (each symbol procs separately) they receive a 1-2 second chill and if they try to leave they receive a 1 second immobilize.
It creates this idea of symbols having a sort of wall which gives enemies a chill when they enter or an immobilize when they leave.