For the a bit more than the cost of an ELC player, DLR provides someone who can go out there and not make glaring mistakes. He can fill in when injuries occur, sit in the press box and not complain, and if someone like Kostin suddenly catches fire and deserves a call up, can go through waivers and the team doesn't miss a beat.
A lot of teams would love to have depth players that are basically cheap and risk free and can be tossed on the waiver wire and be picked up and off your cap table if the need arises.
Then again, Sundqvist was pretty much at this same crossroads and suddenly he became a much better player that his is today in one season. Worth a gamble to see if they can catch lightning in a bottle twice. Unlike PRV who didn't really do anything well except for repeated wrap around attempts that never worked, DLR can play a clog up defensive game which works with the Blues schema.