Blueline - is a critical speed for safe flight should any one engine fail.
Could we take a step back for this?
Blueline = Vyse = best rate of climb single engine
Low speed Redline = Vmca = minimum control speed with one engine inoperative.
I would agree that flying a circuit much below blueline is not ideal, but it is safely possible. If you're flying something fast in the circuit with somethings slow, some adjustment to the circuit is going to be needed. I'm sure it's a no no to pass in the circuit, so, yes, first come first served!