Tested Heartbreaker's Proc Speed

TLDR: Heartbreaker's proc fires 2 streams of missiles even at a single target, 10 missile per stream, over 4 seconds.

Since I got Heartbreaker, I have wanted to know how her proc works.  The text says it fires every .3 seconds for 4 seconds.  The game has ticks of .2 seconds.  So what does that mean?  Does the proc fire 13 times?  14?  Or maybe 10?

Also, the proc has two streams of damage.  I also have wanted to know how that works if there is just one target.  Do both fire just at it?  Or is one nullified?  (I expected the former.  But worth testing.)

The test was a normal Boss 3 run, done twice on two subsequent days.  In both cases, my team was just two heroes.  One is PD.  The other is either Phantom King, or Heartbreaker.  In both cases I added Angi to the team to heal and protect PD.  PD has Berserk 8, the Blitz Scroll, and Revite 4 for maximum ramp speed.  Neither PK nor HB has any extra-hit talent or crest.

Here's the teams and their results.

Heartbreaker:

Testing Heartbreaker

Result: 94,734,436 damage.

Heartbreaker result.

Phantom King:

The control: Phantom King

Result 95,073,376 damage:

Phantom King result.

These two results differ by about .35%, or looked at another way, about a half second of damage for either team.  As such, they are well within experimental variance caused by my drop, critical hits which happened before PD fully ramped, etc.  Thus, the two heroes must be doing the same number of hits per second.  Since PK hits 10 times per second, so must HB.  The model best fitting this is 2 streams, each one hitting each .4 seconds.

 Thus I conclude as per the TLDR.  For fights with (a) max speedup, and (b) low damage caps, PK and HB are practically identical in damage.  If either condition does not obtain, then HB is the superior DPS machine.