I still try to avoid the "ping ponging" of units, I just want to run them off the board or out of the BSB bubble. Running them down if they roll low is swell too.
I'm playing charges differently than everyone it seems. In my "charge" sub-phase of movement, I'm declaring each charge and asking the opponents to choose their charge reaction, then go to the next unit etc etc until all charges have been declared. Then I roll for charge range for each unit.
I'm not sure this "ping ponging" is a valid tactic like some of your are saying, or forcing a unit to flee more than once per turn.
The reason I say this is because of pg. 18, where it describes "Roll Charge Range and Move Chargers".
Notice it says "With all the charge reactions declared and resolved, it's time to see whether or not the charges were successful......."
If you read that entire section it mentions units having to deal with multiple charges.
Also, above the "Roll Charge Range and Move Chargers" section in italics it runs through a scenario where a high elf unit makes three charge reactions, and the final reaction is to flee. The first two charges can redirect, but they don't get to force the high elves to roll flee distance three times.