Neophenx de Chrysalya
I give Trace a 7. As mentioned already, it can be good with a strategic switch-in, but other than that it's an ability that just floats under the radar for most, especially since it's available on so few Pokemon. Even then, a lot of popular abilities wouldn't really help them tremendously to begin with, like Moxie, Levitate, and Weather Abilities. I personally like Trace, but to be used to its greatest potential requires very specific execution and depends a little bit on what the opponent is using against you.
I think thats the whole thing about trace, its so limited and brings up the question is a DW ralts worth it?
or evolving a porygon 2
moxie would be worthless on all the trace pokemon
unless they wanna make a gallade with trace then moxie would be a god send
levitate would have some merit if you can start levitating before somethign with earthquake or worst STAB earthquake shows up
the weather making abilities would be awful for tracing
but weather enhancing abilities like swift swim or sand rush, in the right weather can at least give the pokemon a new life
though I would love to be able to swipe a contact ability
like poison point or flame body
or even cursed body