I personally Mix it up,
Main Arcane Frost with POM > Frostbolt. Traded the pet for POM. I like having the one as frost for the slowing effects. & before they gave all mages Iceblock it was useful to have that on my "Main".

3 alts 40arc/21 Fire through blastwave.

Trinket>AP>POM>Pyroblast = dead somebody.

Timing differences between Frostbolt & Fireball are a non issue IMO as I don't stand around long enough to cast Fireballs anyway.

Instant arcane explosion melts unprepared groups, but is not so effective in arena's against experianced teams. Great for BG's though.