I have a corn feeder in northern Live Oak county I put up about 12 yrs ago now. Put a T-post on each of the 4 legs(5-6" round pad under each). I need to take a pic to show much it has sunk and leaning with a T-posts helping to hold it up. That blind is a lot of weight and it will catch a lot of wind. All it takes is a good rain and high wind together and it will sink. I put a 4'x4' blind up without anything under the legs just like yours. The downwind legs sank in a heavy rain with high winds, I was lucky that it did not turn over. That was in the Hill Country.
I hate to see someone spend a lot of money to build a blind only to have to turn over when conditions get bad. I guess I take more precautions and tend to over do things since I have seen to many high dollar blinds laying on the ground in pieces.
The only thing that may save me is the legs are angled and the stair stringer should act as an anchor on one side. Hopefully its still standing when I go back. We have had blinds out there with drill stem towers in the same spot that haven't sunk but you never know.