I don't know about the guards respawning but before 2.3 I was able to solo the last boss pretty easily. After 2.3 I'm not able to hit the dragon while its in the air making the fight so much more difficult. Before I would just pull the two guards back to the other side of the bridge, kill them there and Vazruden would drop off dragon and just stand there while I killed dragon in the air. Now I have to kill him first(which I cant do fast enough) and the dragon will come down and I have both of them on me.
Makes me mad, because it was an easy way to get three small pris. shards a run. Now I only get one a run by killing Omar(which is extremely easy).