So was Di resta running a dry setup on the other FI? It's the only way to explain the pace difference between the 2.
As for Senna... I don't think he has anything to be sorry about personally. He was in the middle of a legitimate move on the FI. As Vettel went around the outside he might have used a bit more caution before heading to the apex.
Could possibly have been... either that or just not as comfortable in those conditions, or a bit of both.