Honestly if I find myself in a situation where people aren't letting themselves get executed I go for a backline assassination attempt with the class. To be really petty about this I would choose a full hp target just to catch everyone off guard. I did come up with a burst specifically for that moment.

There's also executing those that are in guard with the LB. However, I personally don't go for that, because I think the interaction between the LB and the Guard ability is bugged.