Every day your Bodyguards lose 1 hp a night, lowering his health.  Traditionally, all this did was make him easier to kill, but did not alter his performance in any way.  The health of the bodyguard is now factored in when checking your defense. 10BGs at 50% health provide the same defense as 5 BGs at 100% health.

So that this did not come in as an overnight game changer, anyone who had BGs that were under 80% health, was given a one time heal back up to 80%.

To help offset the 80% heal for those below 80%, those of you who have maintained their BGs, have been given a refund equivalent to the 12,000 * average HP increase to get the site to 80% * number of bodyguards. In addition, all BG's that were 80% or above before the change, were brought to 100%

Sure, I'll put this into the mix.

"As an add on, any chance of having a 'total vitality' or 'active bg'
counter? Obviously it's possible to manually calculate it, but keying up
to 100 or so individual scores into a spreadsheet just to find the
active number will/would be a pain."

BG Equivalent: 4.9 BGs (98.4% Effectiveness of 5 BGs)

The above has been added on to the BG Management page.  This will give you a quick-glance answer to how well your BGs are situated.