Admittedly I am not a Q400 expert but why would you need to maintain V2 speed to the EO altitude in a normal 2 engine condition?
Single engine climb performance is predicated on the engine failing after V1 when the aircraft is still on the ground (or just lifting off). During a normal takeoff with 2 engines, there is extra energy available for the climb. This energy typically turns into extra airspeed - i.e. energy - that will help the airplane to climb if an engine fails after liftoff. I've watched and conducted thousands of normal takeoffs in my career, all of them on 2 engines, and I have never seen an intentional effort to maintain V2 all the way to the EO altitude. Even more disconcerting, I have never seen an SOP that requires pilots to conduct the takeoff with a rotation rate that raises the risk of a tail strike in an effort to maintain a speed that you don't need to maintain in a 2 engine condition.