When using traditional (a.k.a. continuous or "fly") sparging, it helps to raise the mash bed to between 160F and 168F via a mash-out infusion of boiling water before sparging. Additionally, you should shoot to collect a gallon of runoff every 7 to 8 minutes until you become familiar with your setup. You will eventually find its sweet spot.
With that said, mash tun design plays a bigger role in the outcome of a continuous sparge than it does in the outcome of a batch sparge. What are you using for a false bottom?
Could post a photo of your grist? The proper crush for continuous sparging is different than the proper crush for batch sparging.
My mill is permanently set at 45 thousandths of an inch. The non-embossed portion of a credit card will easily pass through my mill (most credit cards are 30 thousandths of an inch thick). However, my average mixed-grist extraction rates are 30 points per pound per gallon with domestic malt and 32 points per pound per gallon with imported malt (both of which are well over 80% considering that they are mixed-grist, not base malt extraction rates). The relatively coarse crush that get with my mill leaves more of the husk intact, which improves the permeability of the mash bed. Uneven permeability is not that big of an issue with batch sparging because the sugars are stirred into suspension. With continuous sparging, the sparge water has to flow evenly through the entire mash bed in order to achieve high extraction rates.
Finally, did you ensure that there were no dough balls in your mash?