How long was it in primary? alot of brewers have this fear that if it sits in primary to long there beer will magically go bad. i have never had a problem fully fermenting out in a carboy, and my secondary is used just to clarify the beer, not let it ferment fully (lotsa bubbles on top).
If it is still fermenting i say let it go if you have notices no problems with the batch itself, if you do like where it is at you can crash cool it so the yeast will settle out and slow down its process.
Another method is to use potassium sorbate and then cool crash it.
wyeast 1084 is a beast, but with you gravity at 1.016 is seems to be doing its job just fine, maybe a little slow though. Next time you make this batch i would raise the starting yeast cell count, either by adding in another smack pack or making a starter, that way it will get off to a better start faster and finish sooner.