Hey Red Dryad how are you doing? Long time no see.
I agree with Allendor, I have sandwiched big units before, and with hit and run just fly away to do it all over again. Ahh the little things in life that make you happy (hit and run being one of those).
It does make you happy,
Furthermore the nice part about a unit of three is people tend to ignore them. That means bye bye war machine, or good luck enemy mage I am coming after you.
This is true they don't seem to draw attention especially with a dragon on the field.
Also now with the new 8th victory conditions you can lose 2 of the 3 and then hide the 3rd and the enemy dosen't get ANY points.
My Avatar is still looking good to me.
Nalwood said with a unit of 6; Counts as two complete ranks, so can take away rank bonus with a flank attack
This is a valid point and I would consider this the PRO of having a unit of 6 vs 2 units of 3. But consider this.
Yes it would take away the rank bonus this is called "disruption" but
only if all 6 survive the 1st round of combat, if you loose one no disruption.
A unit of 3 hitting from the rear would gain CR+2, from the flank CR+1 if at least one model survives. Thats something to consider due to the fact that WHR only have a 6+ save.
(Edit; removed misleading info)
No amount of planning can ever replace dumb luck.