Stuck in the grind.

I am in a cunundrum. I have 400k free xp and I am planning on finishing out the Concept 5 line all the way to 11. I could do it right now. I have partially blueprinted the Consept 5 and unlocked the gun on the gsor 1006. But I have not. I want all the teir 11s eventually. I sit down to play and overthink everything. "If I just keep playing the gsor it is like earning straight fxp." I remember when I had none. The bad old days when I was grinding a stock is3 with the stock gun. The gsor is better than that but not by much.

So here is the question: am I doing it right? Is it better eat my cake or have it? Is the Executor worth the effort of 400k fxp? I get it mostly the slow way.