Never do a tapered leader with a sinking line, as it affects the sink rate of the fly. For starters, you have mono (floats where flouro sinks) in 25lb test. 25lb test is very large diameter, which will sink slower due to more resistance on the line. Combine this with it being mono, that portion of your leader will be higher in the water column then the flouro portion of the leader.
As the mono portion is being held higher in the water column, this will effectively hold the 10 lb flouro up and prevent it from sinking as quickly as it should, leading to holding up the fly. this will not only make the whole set up sink longer, but makes knowing your depth a lot harder.
I think it would also impact the action of the fly, causing unweighted flies to be pulled up (rather then "swim straight") and weighted flies to also be pulled up but sink slower. Again depth is being impacted.
Am I correct in assuming that your fly line sunk faster then the butt section causing an n like shape?