If you're doing pvp, I wouldn't worry about improved scorch. Your targets won't be alive long enough do be debuffed.
Arcane focus is a waste of points, unless you're casting arcane missles all the time, or suicide AOEing. But, you also have flamethrowing, and burning soul, which leads me to belive you are relying on fire to deal damage. Here's what I would do for a blastwave build.
POM/PYRO with blastwave I find most of my problem fights are with casters, not melee. Arcane resiliance is lame upon lame, for reasons discussed ad naseum on the oboards and here. Improved dampen magic is lame as well, but better than nothing. Same with magic absorbtion.
In pvp, the more instants the better, so imp fire blast is a must have. As far as burning soul, you have imp arc missiles if you're getting beat on. Obviously, the aggro mitigation is worthless in pvp. That also makes the addition of incinerate possible. Impact is a 1/10 bet at best, so making it slightly less reliable shouldn't really be noticed. You shouldn't be counting on it anyway, but it's great when it procs. My two cents.