Ive seen issues similiar (non EF related). Not that this has much to do about EF, but I was playing around in Worldbuilder, I put down the Tiger Ace tank from the 'Autry' Mission, and played around with it myself (it didn't have the armor or health and abilities in the campaign) and one thing I also noticed is that it had taken forever to kill a Sherman or M8 (it has a weird bug that makes its damage much lower)