The issue with these guys is not whether they can fly it's their soft skills, leadership and management, abilities that you either have or don't have.
The reason they came from an RJ is because they started there as 200 hour co-pilots, they haven't flown 737's or A320's because they didn't have the experience at the time. Some of them, with the right attitude perform no different to any other pilot however with the others there is a tendency to be weak in the skills required to be a Captain.
Mark my words, EK will still be experiencing this in years to come. There is even a distinct difference between the new joiners from Jet2.Com, Easy jet and Ryan Air. The foundation training, from each airline is remarkably different and very noticeable, Jet2 and easy jet are much better trained than Ryan air guys - it goes with the territory!
My prediction is that DEC's will be employed in this airline for years to come.