I started out using a pump to recirc during mash, now I don't. If you are not careful with your recirculating flow rate you will end up pulling too hard below the bag and create an air pocket. If you create an air pocket, you run the risk of your element scorching (been there done that). You won't have any scorching issues so long as the element is fully immersed.
Now, I bring the water up to mash in temps with the pid controller while recirculating (my temp sensor is in the outlet of the kettle), turn off the pump drop in the grains, then set the pid on manual control at about 5-6%. I don 't recirc during mash, just come around every 15-30 minutes and stir. My mash efficiencies run in the 82% range and this is over the last 10-12 batches. Total brewhouse efficiencies in the 75% range. I will use the pump to recirculate during chilling with an immersion chiller, helps speed up the chilling process and with the temp sensor in the outlet T, I can dial in my pitching temps.
Read around, there are a lot of other things that affect your efficiencies. Just "recirculating" is not a recipe for better efficiencies.