Actually what you're measuring isn't far off.
The T11 has a "typical max SWR of 1.8" but that's not guaranteed, and most of your readings are below that.
I don't have a T11 but do have a T8 and also had a T6 and noted the coax positioning is pretty critical. Tennadyne in their original instructions (mine was made in Texas, part of the "original" Tennadyne line) recommended tying the coax to the lower boom and running it along the lower boom from the feedpoint back to the center bracket.
I tried that, and SWR was bouncy, and there was common mode current coming back down the shield. So, I rearranged the coax routing based on what I'd seen in many military and commercial LPDA applications, where they let the coax "droop" from the feedpoint down to several feet below the antenna, only pulling it back up towards the antenna at the center bracket where it then forms a loop to go down the tower or mast.
Common mode issues went away, and SWR was flatter: So, I left it that way, forever.