Your AOE rotation is more of the Unholy tanking one. As frost your AOE rotation should not involve either pestilence or PS.
Instead glyph for howling blast (so it inflicts those hit with FF), DnD and BB to pop that last blood rune for Blade Barrier. At this point, burn your RP as Frost strikes. (assuming thus far you are macroing in RS to all your abilities)
A good hit with HB is around 2k...can crit for much higher. In short this ability is some serious snap threat and since it adds FF (with glyph) it can power up your BB so it lays out about 700-1k damage per target.
PS is *maybe* nice for single target threat, but not so great for Multitarget threat as a frost tank.