Comparing a engineer type unit with mainline infantry units make little sense to begin with.
Cheap RE have been tested it resulted in RE blobs with weapon punching above their price especially since the get a big accuracy bonus in vet 1.
December Balance
"Rear Echelons
We have scaled up Rear echelons up slightly to reduce spam.
Rear echelons cost up from 160 to 200
Rear echelon rifle damage up from 8 to 10"
As long as rack weapon with full DPS (even being better in their hand by vet 1), are available to RE this issue will exist.
I definitely agree about the rack problem (especially since volley fire actually becomes somewhat useful with a 1919 or BAR) but please don't cal REs mainline inf. They can barely beat pios at midrange.