What steps will reproduce the problem?
1. Cast any spell
2. Cast Pyroblast!
3. Cast any spell

When i watch the time-between-casts i notice that pyroblast! is not counted as cast. Forgive my poor english, ill try to explain with examples :)
Casting fireball -> fire blast -> fireball, in perfet case gives 0 ms -> 0 ms -> 0 ms
While casting fireball -> HS-Pyro -> fireball, in perfet case gives 0 ms -> 1500-ish ms (only 2 numbers = only 2 casts counted, yet actualy 3 spells been casted)
There is no time-between-casts shown between fireball and pyroblast! and upon casting next fireball it says 1500-ish ms time-b-c
This occurs 100% of the time. Also happens when casting any other spell -> hs-pyro -> anyspell.

Guessing you missed the < ! > mark?
Pyroblast   = 3.5 sec cast
Pyroblast!  = instant cast & mana free (procs of Hot Streak talent)

Version is: DPSTime 1.6.1 Stable r33 @ wow-4.0.3