There is some temp fluctuation in every cooker as the fire dies down and more fuel has to be added. But, when you consider that the meats are cooking for hours, does it really matter? It's the average temperature that really matters.
Also, the placement of the Maverick probe in the FEC makes a big difference. If it was near the front edge of one of the racks you will see a bigger variation in temperature than is it were in the middle of the rack. There is a small gap at the front where heat can come up around the heat shield and that will vary more than the area above the heat shield.
As far as the smoke flavor, I've posted this before, so forgive me if you've read it before
Yes, it is not as strong as some other cookers, but I have tasted competition meats cooked on and FEC and on a Jambo (probably the hottest competition cooker right now) and no one in the group could taste a difference in the smoke flavor. Also, in 6 years of cooking on my FEC-100 no one has complained about a lack of smoke flavor. This includes the general public, other BBQers, other comp cooks and a whole lot of judges.