Is the HRV simplified meaning it is installed using the ductwork from a furnace to distribute the air through out the house?  Generally the HRV balancing is not dependent on any hot water heaters.

I think you are overthinking it. Only a very skilled installer would be thinking about that. I think you'd be lucky to see an HRV that was balanced, or remained balanced in an existing home.

Many things could potentially change the balance of an HRV, even doing air-sealing on a home.  Moving to a fan driven venting system will likely change things a bit and technically speaking the HRV should be re-balanced. I would say an independently-ducted HRV is more susceptible than one tied into a forced air furnace.

In independent systems even opening a window will also change the balance of a system, so it comes down to how much change is too much.  The company that installed my HRV likes to slightly over pressure intake to keep a positive pressure environment in the house... but only slightly.  It would certainly be interesting to see some data on this. 

And yeah... it might be overthinking but, with houses getting tighter all the time, this might be more important than we think.