The guards initiate combat, which means he can get in a free blind. The Nightwalker (initially) does not.
If after flee, he waits one side to try sleep spam again, that is an idea. The warrior can not dash immediately from the Nightwalker, but could flee/dash or flee/quaff if lucky to the other side. It works better if there's more annoying guards coming in, forcing the target to flee. Of course for this help you take a risk on obtaining the charge.

Trip, as I said, is not worthwhile for stopping the warrior switching targets 1 vs 1.
Trip always does more lag on you than on the target unless you are a class with cheap shot.
They will get a command in and then destroy this particular AP in a few rounds. (Unless you are well prepped, high charges, they are in fine leather, etc)
In other fights, paladin doesn't even need to switch targets...just wrath. The damage output isn't high enough by the AP in this situation.

All this risk is better controlled with dirt kick or blindness, and then run run if it doesn't work.