HA! ok not sure why or how it fixed itself ...
but after posting I restarted my computer, loaded my save game.
Now my tanks are actually performing as expected....
1 or 2 hits are actually registering damage now, or destroying the hull or turret... Soooooo much easier then having to score 10 or 12 hits to kill a tank.
.... soooo strange.
Hope Muttley your game got fixed too.... this mission is sooo much more fun when your armor isn't bugged/glitched.....