This is one of the strangest issues we have ever seen.
But what ever is happening here is out of the scope of what our own code can be causing.
However we updated Unity and other middleware since last Patch and we are going to release a new Patch this weekend.
We just hope that this will fix the problem for you (fingers crossed).
Please let us know if it helped, once it is out.

For now I changed it so that they flee focussed on getting home and ignore attacks entirely in the process

Hrm this doesn't look too good, seems like one of Unity3d's incompatibility issues with OSX.
However they constantly do fix these and we always update to newest stable version they release.
Recently there were some OSX issues but they fixed most of them so that we don't get reports like yours in the last weeks.
But we have hopes that meanwhile your issue got fixed by Unity as well.

So we hope that the new Patch we are releasing at the end of this week does resolve this issue for you.
If not please let us know, then we need to reach out Unity Technologies support to make them aware that there are still issues.

I am sorry for inconvenience but also we depend on third party software which has sometimes issues on certain system configurations.
Hope it will be sorted this weekend.

Alright :)

Related ticket http://brightrockgames.userecho.com/topics/1414-vampires-arena/

Agreed.
Josh Bishop what shall we do about this?

Nah they regen blood need in and outside Arena afaik they would always fight forever.
Arena is just making it worse by supressing his blood need entirely.

But their blood need and their health, both regenerate while attacking.
If you imagine any battle with only Vampires it would last forever.

Not anymore :)